The climate of Pennsylvania is diverse due to the multitude of geographic features found within the state. Straddling two major climate zones, the southeastern corner of Pennsylvania has the warmest climate. A portion of Greater Philadelphia lies at the southernmost tip of the humid continental climate zone, with the city proper being in the humid subtropical climate zone. Still, Philadelphia features colder, snowier winters than most locations with a humid subtropical climate. Moving west toward the mountainous interior of the state, the climate becomes markedly colder, the number of cloudy days increases, [1] and winter snowfall amounts are greater.
Using the January freezing isotherm, the humid subtropical climate (Cfa) only exists in parts of Greater Philadelphia and low-lying areas of the lower Susquehanna Valley from Harrisburg downriver. Pennsylvania's hardiness zone ranges from 5a in high-elevation areas to 7b in parts of Delaware and Philadelphia Counties.
Western areas of the state, particularly cities near Lake Erie, can receive over 100 inches (254 cm) of snowfall annually, and the entire state receives an average of 41 inches (1,041 mm) of rainfall every year. Floods are more common in March and April than other months of the year. [2]
Tropical cyclones normally threaten the states during the summer and fall, with their main impact being rainfall. [3] Although Hurricane Agnes was barely a hurricane at landfall in Florida, its major impact was over the Mid-Atlantic region, where Agnes combined with a non-tropical low to produce widespread rains of 6 inches (150 mm) to 12 inches (300 mm) with local amounts up to 19 inches (480 mm) in western Schuylkill County in Pennsylvania. [4] These rains produced widespread severe flooding from Virginia northward to New York, with other flooding occurring over the western portions of the Carolinas.
Philadelphia has received sustained winds approaching hurricane-force from tropical cyclones in the past. [5]
The state record low is −42 °F (−41 °C), recorded at Smethport on January 5, 1904, while the state record high is 111 °F (44 °C), recorded at Phoenixville on July 9 and 10, 1936.
Climate data for Pennsylvania | |||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Month | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Year |
Record high °F (°C) | 85 (29) | 83 (28) | 92 (33) | 98 (37) | 102 (39) | 107 (42) | 111 (44) | 108 (42) | 106 (41) | 100 (38) | 88 (31) | 82 (28) | 111 (44) |
Record low °F (°C) | −42 (−41) | −39 (−39) | −31 (−35) | −5 (−21) | 10 (−12) | 20 (−7) | 28 (−2) | 23 (−5) | 17 (−8) | 7 (−14) | −15 (−26) | −29 (−34) | −42 (−41) |
Source: https://climate.met.psu.edu/data/state/staterecords.php |
Event [6] | Measurement | Date | Location |
---|---|---|---|
Greatest 24-Hour Rainfall | 13.50 inches (343 mm) | June 22, 1972 (during Hurricane Agnes) | York |
Note: While the official measured rainfall record is given above, the NCDC notes that an estimated 34.50 inches (876 mm) of rain fell in 12 hours near Smethport on July 17, 1942. The NCDC says this is "arguably the greatest 24-hour rainfall on record outside of the tropics". [6]
Event [6] [7] | Measurement | Date | Location |
---|---|---|---|
Greatest 24-hour snowfall | 38.0 inches (97 cm) | March 20, 1958 | Morgantown |
Greatest two-day snowfall | 60.5 inches (154 cm) | December 24–26, 2017 | Erie |
Greatest snow depth | 60.0 inches (152 cm) | March 22 & 23, 1958 | Gouldsboro |
Event [8] | Measurement | Date | Location |
---|---|---|---|
Wettest Tropical Cyclone | 19.00 inches (483 mm) | Agnes (1972) | Western Schuylkill County |
Month | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Year |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Record high °F (°C) | 72 (22) | 81 (27) | 87 (31) | 93 (34) | 97 (36) | 100 (38) | 105 (41) | 100 (38) | 99 (37) | 93 (34) | 81 (27) | 72 (22) | 105 (41) |
Mean maximum °F (°C) | 60.2 (15.7) | 60.6 (15.9) | 70.6 (21.4) | 83.2 (28.4) | 89.3 (31.8) | 92.6 (33.7) | 94.8 (34.9) | 92.8 (33.8) | 89.2 (31.8) | 80.4 (26.9) | 70.9 (21.6) | 61.7 (16.5) | 95.9 (35.5) |
Mean daily maximum °F (°C) | 38.4 (3.6) | 41.6 (5.3) | 50.8 (10.4) | 63.4 (17.4) | 73.5 (23.1) | 81.9 (27.7) | 86.4 (30.2) | 84.3 (29.1) | 77.4 (25.2) | 65.5 (18.6) | 53.8 (12.1) | 43.1 (6.2) | 63.3 (17.4) |
Daily mean °F (°C) | 30.1 (−1.1) | 32.4 (0.2) | 40.7 (4.8) | 51.8 (11.0) | 62.0 (16.7) | 70.9 (21.6) | 75.6 (24.2) | 73.6 (23.1) | 66.3 (19.1) | 54.6 (12.6) | 43.9 (6.6) | 35.0 (1.7) | 53.1 (11.7) |
Mean daily minimum °F (°C) | 21.8 (−5.7) | 23.2 (−4.9) | 30.5 (−0.8) | 40.3 (4.6) | 50.6 (10.3) | 59.9 (15.5) | 64.7 (18.2) | 62.8 (17.1) | 55.2 (12.9) | 43.8 (6.6) | 34.1 (1.2) | 26.8 (−2.9) | 42.8 (6.0) |
Mean minimum °F (°C) | 4.2 (−15.4) | 5.9 (−14.5) | 14.1 (−9.9) | 25.9 (−3.4) | 35.3 (1.8) | 46.5 (8.1) | 53.7 (12.1) | 51.1 (10.6) | 39.9 (4.4) | 28.7 (−1.8) | 19.1 (−7.2) | 11.7 (−11.3) | 1.8 (−16.8) |
Record low °F (°C) | −15 (−26) | −12 (−24) | −5 (−21) | 12 (−11) | 28 (−2) | 39 (4) | 46 (8) | 41 (5) | 30 (−1) | 21 (−6) | 3 (−16) | −8 (−22) | −15 (−26) |
Average precipitation inches (mm) | 3.30 (84) | 2.77 (70) | 3.63 (92) | 3.67 (93) | 3.65 (93) | 4.40 (112) | 5.30 (135) | 4.56 (116) | 4.84 (123) | 4.14 (105) | 3.24 (82) | 3.86 (98) | 47.36 (1,203) |
Average snowfall inches (cm) | 9.8 (25) | 10.8 (27) | 6.3 (16) | 0.5 (1.3) | 0.0 (0.0) | 0.0 (0.0) | 0.0 (0.0) | 0.0 (0.0) | 0.0 (0.0) | 0.2 (0.51) | 0.9 (2.3) | 4.6 (12) | 33.1 (84) |
Average extreme snow depth inches (cm) | 6.4 (16) | 7.9 (20) | 4.9 (12) | 0.3 (0.76) | 0.0 (0.0) | 0.0 (0.0) | 0.0 (0.0) | 0.0 (0.0) | 0.0 (0.0) | 0.2 (0.51) | 0.6 (1.5) | 2.9 (7.4) | 12.4 (31) |
Average precipitation days (≥ 0.01 in) | 11.4 | 10.1 | 10.9 | 11.8 | 12.4 | 11.4 | 11.0 | 10.2 | 9.6 | 9.9 | 8.9 | 11.5 | 129.1 |
Average snowy days (≥ 0.1 in) | 5.1 | 4.3 | 2.6 | 0.3 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.5 | 2.9 | 15.7 |
Average relative humidity (%) | 70 | 66 | 62 | 61 | 66 | 68 | 70 | 72 | 74 | 72 | 70 | 71 | 69 |
Percent possible sunshine | 43 | 48 | 53 | 47 | 54 | 63 | 57 | 56 | 54 | 53 | 45 | 42 | 51 |
Source: NOAA (relative humidity 1981–2010) [9] [10] [11] |
Climate data for Erie, Pennsylvania (Erie International Airport), 1991–2020 normals, extremes 1873–present | |||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Month | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Year |
Record high °F (°C) | 73 (23) | 77 (25) | 82 (28) | 89 (32) | 91 (33) | 100 (38) | 99 (37) | 96 (36) | 99 (37) | 89 (32) | 82 (28) | 75 (24) | 100 (38) |
Mean maximum °F (°C) | 58.9 (14.9) | 58.5 (14.7) | 69.1 (20.6) | 79.6 (26.4) | 85.1 (29.5) | 90.2 (32.3) | 90.5 (32.5) | 89.8 (32.1) | 87.1 (30.6) | 79.3 (26.3) | 68.4 (20.2) | 59.7 (15.4) | 92.4 (33.6) |
Mean daily maximum °F (°C) | 35.2 (1.8) | 36.5 (2.5) | 44.3 (6.8) | 56.8 (13.8) | 68.3 (20.2) | 77.1 (25.1) | 81.1 (27.3) | 79.9 (26.6) | 73.7 (23.2) | 62.3 (16.8) | 50.5 (10.3) | 40.2 (4.6) | 58.8 (14.9) |
Daily mean °F (°C) | 28.2 (−2.1) | 28.9 (−1.7) | 36.1 (2.3) | 47.4 (8.6) | 58.8 (14.9) | 68.2 (20.1) | 72.7 (22.6) | 71.5 (21.9) | 65.2 (18.4) | 54.3 (12.4) | 43.6 (6.4) | 34.1 (1.2) | 50.8 (10.4) |
Mean daily minimum °F (°C) | 21.3 (−5.9) | 21.4 (−5.9) | 27.9 (−2.3) | 38.0 (3.3) | 49.3 (9.6) | 59.4 (15.2) | 64.2 (17.9) | 63.2 (17.3) | 56.7 (13.7) | 46.3 (7.9) | 36.7 (2.6) | 28.0 (−2.2) | 42.7 (5.9) |
Mean minimum °F (°C) | 3.6 (−15.8) | 4.1 (−15.5) | 11.2 (−11.6) | 25.7 (−3.5) | 35.3 (1.8) | 45.7 (7.6) | 53.8 (12.1) | 53.0 (11.7) | 44.4 (6.9) | 33.9 (1.1) | 23.8 (−4.6) | 13.3 (−10.4) | 0.2 (−17.7) |
Record low °F (°C) | −18 (−28) | −18 (−28) | −9 (−23) | 7 (−14) | 26 (−3) | 32 (0) | 44 (7) | 37 (3) | 33 (1) | 23 (−5) | 6 (−14) | −11 (−24) | −18 (−28) |
Average precipitation inches (mm) | 3.41 (87) | 2.52 (64) | 3.08 (78) | 3.47 (88) | 3.50 (89) | 3.70 (94) | 3.33 (85) | 3.35 (85) | 4.32 (110) | 4.38 (111) | 3.75 (95) | 4.17 (106) | 42.98 (1,092) |
Average snowfall inches (cm) | 31.8 (81) | 19.4 (49) | 14.5 (37) | 2.6 (6.6) | 0.0 (0.0) | 0.0 (0.0) | 0.0 (0.0) | 0.0 (0.0) | 0.0 (0.0) | 0.1 (0.25) | 9.6 (24) | 26.3 (67) | 104.3 (265) |
Average extreme snow depth inches (cm) | 9.9 (25) | 9.1 (23) | 7.3 (19) | 1.7 (4.3) | 0.0 (0.0) | 0.0 (0.0) | 0.0 (0.0) | 0.0 (0.0) | 0.0 (0.0) | 0.0 (0.0) | 4.8 (12) | 7.6 (19) | 13.8 (35) |
Average precipitation days (≥ 0.01 in) | 19.7 | 15.4 | 14.3 | 14.0 | 13.5 | 11.5 | 10.5 | 10.2 | 10.1 | 14.3 | 14.9 | 18.5 | 166.9 |
Average snowy days (≥ 0.1 in) | 16.3 | 12.3 | 7.8 | 2.3 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.2 | 4.8 | 11.5 | 55.2 |
Average relative humidity (%) | 74.5 | 75.4 | 71.9 | 67.9 | 68.9 | 71.3 | 71.7 | 74.0 | 74.5 | 71.1 | 72.3 | 75.0 | 72.4 |
Source: NOAA (relative humidity 1961–1990) [12] [13] [14] |
Climate data for Harrisburg, Pennsylvania (Harrisburg Int'l), 1991–2020 normals, [lower-alpha 3] extremes 1888–present [lower-alpha 4] | |||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Month | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Year |
Record high °F (°C) | 73 (23) | 79 (26) | 87 (31) | 93 (34) | 97 (36) | 100 (38) | 107 (42) | 104 (40) | 102 (39) | 97 (36) | 84 (29) | 75 (24) | 107 (42) |
Mean maximum °F (°C) | 59.3 (15.2) | 61.4 (16.3) | 72.7 (22.6) | 83.5 (28.6) | 89.5 (31.9) | 93.3 (34.1) | 96.2 (35.7) | 93.8 (34.3) | 89.7 (32.1) | 81.1 (27.3) | 70.8 (21.6) | 62.3 (16.8) | 97.0 (36.1) |
Mean daily maximum °F (°C) | 38.6 (3.7) | 42.0 (5.6) | 51.3 (10.7) | 63.8 (17.7) | 73.7 (23.2) | 82.4 (28.0) | 86.8 (30.4) | 84.7 (29.3) | 77.6 (25.3) | 65.7 (18.7) | 53.9 (12.2) | 43.3 (6.3) | 63.6 (17.6) |
Daily mean °F (°C) | 30.8 (−0.7) | 33.4 (0.8) | 41.8 (5.4) | 53.2 (11.8) | 63.4 (17.4) | 72.5 (22.5) | 77.3 (25.2) | 75.2 (24.0) | 67.9 (19.9) | 55.8 (13.2) | 44.8 (7.1) | 35.8 (2.1) | 54.3 (12.4) |
Mean daily minimum °F (°C) | 23.0 (−5.0) | 24.7 (−4.1) | 32.3 (0.2) | 42.5 (5.8) | 53.1 (11.7) | 62.7 (17.1) | 67.8 (19.9) | 65.8 (18.8) | 58.2 (14.6) | 46.0 (7.8) | 35.8 (2.1) | 28.2 (−2.1) | 45.0 (7.2) |
Mean minimum °F (°C) | 7.4 (−13.7) | 10.1 (−12.2) | 17.9 (−7.8) | 29.2 (−1.6) | 39.6 (4.2) | 50.8 (10.4) | 58.3 (14.6) | 55.8 (13.2) | 45.2 (7.3) | 33.0 (0.6) | 22.9 (−5.1) | 14.6 (−9.7) | 5.0 (−15.0) |
Record low °F (°C) | −22 (−30) | −13 (−25) | −1 (−18) | 11 (−12) | 30 (−1) | 40 (4) | 49 (9) | 45 (7) | 30 (−1) | 23 (−5) | 10 (−12) | −8 (−22) | −22 (−30) |
Average precipitation inches (mm) | 3.03 (77) | 2.59 (66) | 3.70 (94) | 3.55 (90) | 3.83 (97) | 3.98 (101) | 4.74 (120) | 3.77 (96) | 4.83 (123) | 3.81 (97) | 2.97 (75) | 3.43 (87) | 44.23 (1,123) |
Average snowfall inches (cm) | 9.1 (23) | 9.4 (24) | 5.6 (14) | 0.4 (1.0) | 0.0 (0.0) | 0.0 (0.0) | 0.0 (0.0) | 0.0 (0.0) | 0.0 (0.0) | 0.2 (0.51) | 0.8 (2.0) | 4.4 (11) | 29.9 (76) |
Average extreme snow depth inches (cm) | 5.3 (13) | 5.1 (13) | 4.0 (10) | 0.2 (0.51) | 0.0 (0.0) | 0.0 (0.0) | 0.0 (0.0) | 0.0 (0.0) | 0.0 (0.0) | 0.1 (0.25) | 0.3 (0.76) | 2.4 (6.1) | 9.8 (25) |
Average precipitation days (≥ 0.01 in) | 10.9 | 10.4 | 11.0 | 11.4 | 13.0 | 11.5 | 10.9 | 10.0 | 9.2 | 9.2 | 8.5 | 10.3 | 126.3 |
Average snowy days (≥ 0.1 in) | 5.1 | 4.8 | 2.7 | 0.3 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.7 | 2.7 | 16.3 |
Average ultraviolet index | 2 | 3 | 4 | 6 | 8 | 9 | 9 | 8 | 6 | 4 | 2 | 2 | 5 |
Source 1: NOAA [16] [17] | |||||||||||||
Source 2: Weather Atlas (UV data) [18] |
Month | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Year |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Record high °F (°C) | 74 (23) | 79 (26) | 87 (31) | 95 (35) | 97 (36) | 102 (39) | 104 (40) | 106 (41) | 102 (39) | 96 (36) | 84 (29) | 73 (23) | 106 (41) |
Mean maximum °F (°C) | 63.3 (17.4) | 63.5 (17.5) | 73.8 (23.2) | 84.3 (29.1) | 90.2 (32.3) | 94.8 (34.9) | 97.1 (36.2) | 94.8 (34.9) | 90.6 (32.6) | 82.6 (28.1) | 72.4 (22.4) | 64.2 (17.9) | 98.1 (36.7) |
Mean daily maximum °F (°C) | 41.3 (5.2) | 44.3 (6.8) | 52.8 (11.6) | 64.7 (18.2) | 74.4 (23.6) | 83.2 (28.4) | 87.8 (31.0) | 85.8 (29.9) | 78.9 (26.1) | 67.2 (19.6) | 55.9 (13.3) | 46.0 (7.8) | 65.2 (18.4) |
Daily mean °F (°C) | 33.7 (0.9) | 35.9 (2.2) | 43.6 (6.4) | 54.5 (12.5) | 64.3 (17.9) | 73.5 (23.1) | 78.7 (25.9) | 76.8 (24.9) | 69.9 (21.1) | 58.2 (14.6) | 47.4 (8.6) | 38.6 (3.7) | 56.3 (13.5) |
Mean daily minimum °F (°C) | 26.0 (−3.3) | 27.5 (−2.5) | 34.3 (1.3) | 44.3 (6.8) | 54.2 (12.3) | 63.9 (17.7) | 69.6 (20.9) | 67.9 (19.9) | 60.9 (16.1) | 49.2 (9.6) | 38.8 (3.8) | 31.2 (−0.4) | 47.3 (8.5) |
Mean minimum °F (°C) | 10.7 (−11.8) | 13.7 (−10.2) | 20.8 (−6.2) | 33.0 (0.6) | 43.1 (6.2) | 53.2 (11.8) | 62.2 (16.8) | 60.3 (15.7) | 49.5 (9.7) | 37.1 (2.8) | 26.4 (−3.1) | 19.0 (−7.2) | 8.6 (−13.0) |
Record low °F (°C) | −7 (−22) | −11 (−24) | 5 (−15) | 14 (−10) | 28 (−2) | 44 (7) | 51 (11) | 44 (7) | 35 (2) | 25 (−4) | 8 (−13) | −5 (−21) | −11 (−24) |
Average precipitation inches (mm) | 3.13 (80) | 2.75 (70) | 3.96 (101) | 3.47 (88) | 3.34 (85) | 4.04 (103) | 4.38 (111) | 4.29 (109) | 4.40 (112) | 3.47 (88) | 2.91 (74) | 3.97 (101) | 44.11 (1,120) |
Average snowfall inches (cm) | 7.1 (18) | 8.4 (21) | 3.6 (9.1) | 0.3 (0.76) | 0.0 (0.0) | 0.0 (0.0) | 0.0 (0.0) | 0.0 (0.0) | 0.0 (0.0) | 0.0 (0.0) | 0.2 (0.51) | 3.5 (8.9) | 23.1 (59) |
Average precipitation days (≥ 0.01 in) | 11.0 | 9.7 | 10.9 | 10.9 | 11.0 | 10.3 | 10.1 | 8.9 | 9.3 | 9.1 | 8.6 | 11.0 | 120.8 |
Average snowy days (≥ 0.1 in) | 4.1 | 3.8 | 2.0 | 0.2 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.1 | 1.8 | 12.0 |
Average relative humidity (%) | 66.2 | 63.6 | 61.7 | 60.4 | 65.4 | 67.8 | 69.6 | 70.4 | 71.6 | 70.8 | 68.4 | 67.7 | 67.0 |
Average dew point °F (°C) | 19.8 (−6.8) | 21.0 (−6.1) | 28.6 (−1.9) | 37.0 (2.8) | 49.5 (9.7) | 59.2 (15.1) | 64.6 (18.1) | 63.7 (17.6) | 57.2 (14.0) | 45.7 (7.6) | 35.6 (2.0) | 25.5 (−3.6) | 42.3 (5.7) |
Mean monthly sunshine hours | 155.7 | 154.7 | 202.8 | 217.0 | 245.1 | 271.2 | 275.6 | 260.1 | 219.3 | 204.5 | 154.7 | 137.7 | 2,498.4 |
Percent possible sunshine | 52 | 52 | 55 | 55 | 55 | 61 | 61 | 61 | 59 | 59 | 52 | 47 | 56 |
Average ultraviolet index | 2 | 3 | 4 | 6 | 8 | 9 | 9 | 8 | 6 | 4 | 2 | 2 | 5 |
Source 1: NOAA (relative humidity, dew point and sun 1961–1990) [22] [23] [20] | |||||||||||||
Source 2: Weather Atlas (UV index) [24] |
Climate data for Philadelphia | |||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Month | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Year |
Average sea temperature °F (°C) | 41.8 (5.5) | 39.9 (4.4) | 41.2 (5.1) | 46.7 (8.2) | 53.9 (12.2) | 66.3 (19.0) | 74.0 (23.3) | 75.9 (24.4) | 71.4 (21.9) | 64.2 (17.9) | 55.1 (12.8) | 47.7 (8.8) | 56.5 (13.6) |
Mean daily daylight hours | 10.0 | 11.0 | 12.0 | 13.0 | 14.0 | 15.0 | 15.0 | 14.0 | 12.0 | 11.0 | 10.0 | 9.0 | 12.2 |
Source: Weather Atlas [24] |
Climate data for Pittsburgh (Pittsburgh International Airport), 1991–2020 normals, [lower-alpha 7] extremes 1874–present [lower-alpha 8] | |||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Month | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Year |
Record high °F (°C) | 75 (24) | 78 (26) | 84 (29) | 90 (32) | 95 (35) | 98 (37) | 103 (39) | 103 (39) | 102 (39) | 91 (33) | 82 (28) | 74 (23) | 103 (39) |
Mean maximum °F (°C) | 61.5 (16.4) | 63.2 (17.3) | 73.5 (23.1) | 81.5 (27.5) | 86.8 (30.4) | 90.4 (32.4) | 91.3 (32.9) | 90.3 (32.4) | 88.2 (31.2) | 79.9 (26.6) | 70.8 (21.6) | 62.6 (17.0) | 92.6 (33.7) |
Mean daily maximum °F (°C) | 36.3 (2.4) | 39.6 (4.2) | 49.1 (9.5) | 62.4 (16.9) | 71.9 (22.2) | 79.4 (26.3) | 82.9 (28.3) | 81.7 (27.6) | 75.1 (23.9) | 63.1 (17.3) | 50.9 (10.5) | 40.6 (4.8) | 61.1 (16.2) |
Daily mean °F (°C) | 28.8 (−1.8) | 31.4 (−0.3) | 39.7 (4.3) | 51.5 (10.8) | 61.2 (16.2) | 69.4 (20.8) | 73.2 (22.9) | 71.8 (22.1) | 64.9 (18.3) | 53.4 (11.9) | 42.6 (5.9) | 33.7 (0.9) | 51.8 (11.0) |
Mean daily minimum °F (°C) | 21.4 (−5.9) | 23.2 (−4.9) | 30.3 (−0.9) | 40.7 (4.8) | 50.6 (10.3) | 59.3 (15.2) | 63.4 (17.4) | 62.0 (16.7) | 54.8 (12.7) | 43.7 (6.5) | 34.3 (1.3) | 26.7 (−2.9) | 42.5 (5.8) |
Mean minimum °F (°C) | 1.0 (−17.2) | 5.0 (−15.0) | 11.7 (−11.3) | 25.4 (−3.7) | 35.6 (2.0) | 45.2 (7.3) | 52.5 (11.4) | 51.1 (10.6) | 41.2 (5.1) | 29.5 (−1.4) | 19.3 (−7.1) | 9.7 (−12.4) | −1.5 (−18.6) |
Record low °F (°C) | −22 (−30) | −20 (−29) | −5 (−21) | 11 (−12) | 26 (−3) | 34 (1) | 42 (6) | 39 (4) | 31 (−1) | 16 (−9) | −1 (−18) | −12 (−24) | −22 (−30) |
Average precipitation inches (mm) | 2.96 (75) | 2.62 (67) | 3.15 (80) | 3.32 (84) | 3.83 (97) | 4.12 (105) | 4.26 (108) | 3.52 (89) | 3.30 (84) | 2.83 (72) | 2.86 (73) | 2.84 (72) | 39.61 (1,006) |
Average snowfall inches (cm) | 13.3 (34) | 11.7 (30) | 7.6 (19) | 1.0 (2.5) | 0.0 (0.0) | 0.0 (0.0) | 0.0 (0.0) | 0.0 (0.0) | 0.0 (0.0) | 0.4 (1.0) | 2.4 (6.1) | 7.7 (20) | 44.1 (112) |
Average precipitation days (≥ 0.01 in) | 16.8 | 13.9 | 14.0 | 13.9 | 13.5 | 12.4 | 11.2 | 10.5 | 9.8 | 11.1 | 12.0 | 14.6 | 153.7 |
Average snowy days (≥ 0.1 in) | 12.2 | 9.3 | 5.9 | 1.6 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.3 | 3.3 | 7.6 | 40.2 |
Average relative humidity (%) | 69.9 | 67.3 | 64.1 | 59.8 | 63.4 | 66.2 | 68.8 | 71.2 | 72.0 | 68.3 | 70.2 | 71.9 | 67.8 |
Average dew point °F (°C) | 17.2 (−8.2) | 18.9 (−7.3) | 26.8 (−2.9) | 34.5 (1.4) | 45.9 (7.7) | 55.2 (12.9) | 60.1 (15.6) | 59.5 (15.3) | 53.4 (11.9) | 40.8 (4.9) | 32.4 (0.2) | 23.2 (−4.9) | 39.0 (3.9) |
Mean monthly sunshine hours | 93.9 | 108.5 | 155.4 | 182.8 | 217.4 | 242.2 | 254.9 | 228.4 | 196.7 | 167.3 | 99.4 | 74.4 | 2,021.3 |
Percent possible sunshine | 31 | 36 | 42 | 46 | 49 | 54 | 56 | 54 | 53 | 48 | 33 | 26 | 45 |
Average ultraviolet index | 2 | 2 | 2 | 4 | 6 | 6 | 6 | 5 | 4 | 3 | 2 | 1 | 4 |
Source 1: NOAA (relative humidity, dew point and sun 1961–1990) [25] [26] [27] [28] | |||||||||||||
Source 2: Weather Atlas (UV) [29] |
Month | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Year |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Record high °F (°C) | 69 (21) | 76 (24) | 85 (29) | 93 (34) | 93 (34) | 99 (37) | 103 (39) | 102 (39) | 100 (38) | 91 (33) | 81 (27) | 71 (22) | 103 (39) |
Mean maximum °F (°C) | 57.7 (14.3) | 57.0 (13.9) | 68.0 (20.0) | 81.3 (27.4) | 88.0 (31.1) | 90.5 (32.5) | 92.8 (33.8) | 90.5 (32.5) | 87.6 (30.9) | 78.6 (25.9) | 69.1 (20.6) | 59.6 (15.3) | 94.3 (34.6) |
Mean daily maximum °F (°C) | 35.7 (2.1) | 38.8 (3.8) | 47.6 (8.7) | 61.1 (16.2) | 72.2 (22.3) | 79.9 (26.6) | 84.6 (29.2) | 82.4 (28.0) | 75.1 (23.9) | 63.1 (17.3) | 51.2 (10.7) | 40.3 (4.6) | 61.0 (16.1) |
Daily mean °F (°C) | 28.0 (−2.2) | 30.3 (−0.9) | 38.3 (3.5) | 50.2 (10.1) | 60.9 (16.1) | 69.0 (20.6) | 73.7 (23.2) | 71.8 (22.1) | 64.6 (18.1) | 53.2 (11.8) | 42.7 (5.9) | 33.3 (0.7) | 51.3 (10.7) |
Mean daily minimum °F (°C) | 20.3 (−6.5) | 21.9 (−5.6) | 28.9 (−1.7) | 39.3 (4.1) | 49.6 (9.8) | 58.1 (14.5) | 62.7 (17.1) | 61.1 (16.2) | 54.0 (12.2) | 43.3 (6.3) | 34.3 (1.3) | 26.3 (−3.2) | 41.7 (5.4) |
Mean minimum °F (°C) | 0.6 (−17.4) | 3.6 (−15.8) | 11.0 (−11.7) | 24.7 (−4.1) | 34.7 (1.5) | 44.1 (6.7) | 50.9 (10.5) | 48.8 (9.3) | 38.7 (3.7) | 28.7 (−1.8) | 18.0 (−7.8) | 9.1 (−12.7) | −1.6 (−18.7) |
Record low °F (°C) | −21 (−29) | −19 (−28) | −4 (−20) | 8 (−13) | 27 (−3) | 34 (1) | 43 (6) | 38 (3) | 29 (−2) | 19 (−7) | 5 (−15) | −13 (−25) | −21 (−29) |
Average precipitation inches (mm) | 2.59 (66) | 2.07 (53) | 2.77 (70) | 3.26 (83) | 3.26 (83) | 3.80 (97) | 3.61 (92) | 3.85 (98) | 4.15 (105) | 3.71 (94) | 2.85 (72) | 2.80 (71) | 38.72 (983) |
Average snowfall inches (cm) | 11.7 (30) | 10.9 (28) | 10.1 (26) | 0.8 (2.0) | 0.0 (0.0) | 0.0 (0.0) | 0.0 (0.0) | 0.0 (0.0) | 0.0 (0.0) | 0.7 (1.8) | 3.2 (8.1) | 7.7 (20) | 45.1 (115) |
Average precipitation days (≥ 0.01 in) | 12.6 | 11.4 | 11.8 | 12.2 | 12.9 | 12.9 | 11.1 | 11.1 | 10.0 | 10.7 | 10.3 | 12.1 | 139.1 |
Average snowy days (≥ 0.1 in) | 8.7 | 8.4 | 4.8 | 1.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.3 | 1.7 | 6.3 | 31.2 |
Average relative humidity (%) | 70.1 | 67.5 | 63.3 | 60.4 | 64.6 | 70.5 | 71.1 | 73.8 | 75.2 | 71.6 | 71.8 | 72.5 | 69.4 |
Average dew point °F (°C) | 16.2 (−8.8) | 17.2 (−8.2) | 24.4 (−4.2) | 33.1 (0.6) | 45.3 (7.4) | 55.9 (13.3) | 60.4 (15.8) | 59.9 (15.5) | 53.4 (11.9) | 41.4 (5.2) | 32.2 (0.1) | 22.3 (−5.4) | 38.5 (3.6) |
Mean monthly sunshine hours | 130.3 | 143.7 | 185.7 | 210.5 | 246.9 | 269.7 | 285.7 | 257.2 | 200.2 | 173.3 | 104.3 | 95.9 | 2,303.4 |
Percent possible sunshine | 44 | 48 | 50 | 53 | 55 | 60 | 62 | 60 | 54 | 50 | 35 | 33 | 52 |
Source: NOAA (relative humidity and dew point 1964–1990, sun 1961–1990) [31] [32] [33] |
Missouri generally has a variety of seasonal humid subtropical climate, with cool winters and long, hot summers. In the southern part of the state, particularly in the Bootheel, the climate borders on a more mild-type humid subtropical climate, and in the northern third, the state transitions into a humid continental climate. Because of its location in the interior United States, Missouri often experiences extremes in temperatures. Lacking either large mountains or oceans nearby to moderate its temperature, its climate is alternately influenced by air from the cold Arctic and the hot and humid Gulf of Mexico.
The climate of Virginia, a state on the east coast of the United States, is mild compared to more northern areas of the United States such as New England and the Midwest. Most of Virginia east of the Blue Ridge mountains, the southern part of the Shenandoah Valley, and the Roanoke Valley, has a humid subtropical climate. In the mountainous areas west of the Blue Ridge, the climate is warm-summer humid continental or oceanic climate. Severe weather, in the form of tornadoes, tropical cyclones, and winter storms, impacts the state on a regular basis. Central Virginia received significant snowfall of 20 inches in December 2009.
Milwaukee has a humid continental climate, with four distinct seasons and wide variations in temperature and precipitation in short periods of time. The city's climate is also strongly influenced by nearby Lake Michigan, which creates two varying climates within the Milwaukee area. The Urban heat island effect also plays a role in the city's climate, insulating it from winter cold, but keeping it cooler in spring and summer.
The climate of Puerto Rico in the Köppen climate classification is predominantly tropical rainforest. Temperatures throughout the year are warm to hot, averaging near 85 °F (29 °C) in lower elevations and 70 °F (21 °C) in the mountains. Easterly trade winds pass across the island year round while the rainy season stretches from April into November. The relatively cool trade winds are blocked by the mountains of the Cordillera Central which causes rain shadows and sharp variations in the temperature and wind speed over short distances. About a quarter of the average annual rainfall for Puerto Rico occurs during tropical cyclones, which are more frequent during La Niña years.
The climate of California varies widely from hot desert to alpine tundra, depending on latitude, elevation, and proximity to the Pacific Coast. California's coastal regions, the Sierra Nevada foothills, and much of the Central Valley have a Mediterranean climate, with warmer, drier weather in summer and cooler, wetter weather in winter. The influence of the ocean generally moderates temperature extremes, creating warmer winters and substantially cooler summers in coastal areas.
The climate of San Diego, California is classified as a hot-summer Mediterranean climate. The basic climate features hot, sunny, and dry summers, and cooler, wetter winters. However, San Diego is much more arid than typical Mediterranean climates, and winters are still dry compared with most other zones with this type of climate. The climate at San Diego International Airport, the location for official weather reports for San Diego, as well as the climate at most beach areas, straddles the border between BSh and BSk due to the mild winters and cool summers in these locations.
Columbus, Ohio has a humid continental climate, characterized by humid, hot summers and cold winters, with no dry season. The Dfa climate has average temperatures above 22 °C during the warmest months, with at least four months averaging above 10 °C, and below 0 °C during the coldest. The climate is transitional with the Cfa humid subtropical climate to the south, characterized by humid, hot summers and cool winters.
The Climate of Grand Forks, North Dakota is a warm summer continental typical of cities located in the Great Plains, with four very distinct seasons and great variation in temperatures over very short periods of time. The city's climate is characterized by long, cold winters with moderate snowfall and warm summers which are typically humid.
North Dakota's climate is typical of a continental climate with cold winters and warm-hot summers. The state's location in the Upper Midwest allows it to experience some of the widest variety of weather in the United States, and each of the four seasons has its own distinct characteristics. The eastern half of the state has a humid continental climate with warm to hot, somewhat humid summers and cold, windy winters, while the western half has a semi-arid climate with less precipitation and less humidity but similar temperature profiles. The areas east of the Missouri River get slightly colder winters, while those west of the stream get higher summer daytime temperatures. In general, the diurnal temperature difference is prone to be more significant in the west due to higher elevation and less humidity.
The climate of Romania is continental, transitioning into humid subtropical on the eastern coast, influenced by polar intrusions, and therefore characterized by harsh winters. The mountain ranges of the Carpathian arc have a cool mountain climate with high humidity throughout the year.
The climate of Georgia is a humid subtropical climate, with most of the state having short, mild winters and long, hot summers. The Atlantic Ocean on the east coast of Georgia and the hill country in the north impact the state's climate. Also, the Chattahoochee River divides Georgia into separate climatic regions with the mountain region to the northwest being cooler than the rest of the state; the average temperatures for the mountain region in January and July are 39 °F (4 °C) and 78 °F (26 °C) respectively. Winter in Georgia is characterized by mild temperatures and little snowfall around the state, with the potential for snow and ice increasing in the northern parts of the state. Summer daytime temperatures in Georgia often exceed 95 °F (35 °C). The state experiences widespread precipitation. Tornadoes and tropical cyclones are common.
North Carolina's climate is varying, from the Atlantic coast in the east to the Appalachian Mountain range in the west. The mountains often act as a "shield", blocking low temperatures and storms from the Midwest from entering the Piedmont and Coastal Plain of North Carolina.
Anchorage, Alaska has a subarctic climate with the code Dsc according to the Köppen climate classification due to its short, cool summers. The weather on any given day is very unpredictable. Some winters feature several feet of snow and cold temperatures, while the summers are typically mild but are cool compared to the contiguous US and interior Alaska. Because of Anchorage's high latitude, summer days are very long and winter daylight hours are very short. The longest day of sunlight being 18hrs and 21 minutes, and shortest being 5 hours and 28 minutes. Anchorage is often cloudy during the winter, which decreases the amount of sunlight experienced by residents.
South Carolina has a humid subtropical climate, with hot summers throughout most of the state. But, an exception does occur in the Blue Ridge Mountains, as outlier pockets of an Oceanic Climate do exist. Mild winters predominate in the eastern and southern part of the state, but cool to occasionally cold winters are the standard in the northwestern area of the state, especially areas at or above 600 feet in elevation. On average, between 40 and 80 inches of precipitation falls annually across the state, potentially even in excess of 100 inches in portions of the Appalachian temperate rainforest. Tropical cyclones, and afternoon thunderstorms due to hot and humid conditions, contribute to precipitation during the summer and sometimes fall months, while extratropical cyclones contribute to precipitation during the fall, winter, and spring months. The coast experiences nearly all of their tropical weather impacts from storms coming directly from the Atlantic coast. The northwestern area of the state can receive impacts from both Atlantic basin storms moving westward from the coast and also occasionally very heavy rainfall and flooding from storms originating from the Gulf of Mexico that move inland towards the northeast after making landfall from the Florida Panhandle to Louisiana.
The climate of New York (state) is generally humid continental, while the extreme southeastern portion of the state lies in the warmer humid subtropical climate zone. Winter temperatures average below freezing during January and February in much of the state of New York, but several degrees above freezing along the Atlantic coastline, including New York City.
The climate of Miami is classified as having a tropical monsoon climate with hot and humid summers; short, warm winters; and a marked drier season in the winter. Its sea-level elevation, coastal location, position just above the Tropic of Cancer, and proximity to the Gulf Stream shape its climate.
The climate of New Jersey classification of the U.S. state of New Jersey is humid subtropical in South Jersey with a humid continental climate in North Jersey, particularly in the northwestern area of the state. The northwest part of New Jersey is the snowiest due to the higher elevations that earn it a Dfb classification. During the winters, New Jersey can experience Nor'easters, which are snowstorms that affect the Northeastern United States, and Atlantic Canada. However, many would-be snow events in the state end up turning to rain due to warm ocean air being brought in by the storm. New Jersey's climate is shaped by its proximity to the Atlantic Ocean which provides moisture and moderates temperatures. According to climatology research by the U.S. National Oceanic and Atmospheric Administration, New Jersey has been the fastest-warming state by average air temperature over a 100-year period beginning in the early 20th century, related to global warming.
The climate of Allentown, Pennsylvania is classified as a humid continental climate. Allentown's warmest month is July with a daily average temperature of 74.7 °F (23.7 °C) and the coldest month being January with a daily average of 29.4 °F (−1.4 °C). The average precipitation of Allentown is 45.35 inches (1,152 mm) per year.
Washington is the northwesternmost state of the contiguous United States. It borders Idaho to the east, bounded mostly by the meridian running north from the confluence of the Snake River and Clearwater River, except for the southernmost section where the border follows the Snake River. Oregon is to the south, with the Columbia River forming the western part and the 46th parallel forming the eastern part of the Oregon–Washington border. During Washington's partition from Oregon, the original plan for the border followed the Columbia River east until the confluence with the Snake, and then would have followed the Snake River east; this was changed to keep Walla Walla's fertile farmland in Washington.
The climate of New England varies greatly across its 500-mile (800 km) span from northern Maine to southern Connecticut.