A cold wave is a weather phenomenon that is distinguished by a cooling of the air. Specifically, as used by the U.S. National Weather Service, a cold wave is a rapid fall in temperature within a 24-hour period requiring substantially increased protection to agriculture, industry, commerce, and social activities. The precise criteria for a cold wave are the rate at which the temperature falls, and the minimum to which it falls. This minimum temperature is dependent on the geographical region and time of year.
The cold wave of 1978 was a weather event that occurred in the Eastern United States. Beginning in December 1977 and lasting until March, it produced one of the coldest winters on record in all states east of the Rocky Mountains, except Maine.
The 1936 North American cold wave ranks among the most intense cold waves in the recorded history of North America. The Midwestern United States and the Canadian Prairies were hit the hardest. Only the Southwestern United States and California largely escaped its effects.
The 1912 United States cold wave was one of the coldest periods since 1870 in the Northern United States, according to the U.S. National Weather Service. The cold wave started in November 1911 and finally ended in March 1912, with periodic interruptions by milder temperatures.
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 1985 North America cold wave was a meteorological event which occurred in January, 1985, as a result of the shifting of the polar vortex farther south than is normally seen. Blocked from its normal movement, polar air from the north pushed into nearly every section of the central and eastern half of the United States and Canada, shattering record low temperature records in a number of areas. This was preceded by unusually warm weather in the eastern U.S. in December, 1984, suggesting that there was a build-up of cold air that was suddenly released from the Arctic, a meteorological event known as a mobile polar high. Mount Mitchell, in North Carolina recorded an all time record low of −34 °F (−37 °C).
The cold wave of January 1977 produced the only known trace of snow in the greater Miami area of Florida ever reported. It occurred following the passage of a strong cold front, in combination with a high-pressure area situated over the Mississippi River Valley. As a result, cold air moved far to the south across Florida, causing both snow flurries and record low temperatures. Most notably, the weather system brought snow flurries as far south as Homestead on January 19. No snow had ever been reported in southeastern Florida before or since. Damage was most significant to agriculture, as major losses occurred to citrus fruits and tender vegetables. Statewide, agricultural damage from the cold wave totaled to $350 million (1977 USD), and losses overall totaled to $2 billion (1977 USD). One fatality occurred due to an automobile accident in Central Florida, which was related to the cold wave.
The 2013 extreme weather events included several all-time temperature records in Northern and Southern Hemisphere. The February extent of snow cover in Eurasia and North America was above average, while the extent of Arctic ice in the same month was 4.5% below the 1981–2010 average. The Northern Hemisphere weather extremes have been linked to the melting of Arctic sea ice, which alters atmospheric circulation in a way that leads to more snow and ice.
The January–March 2014 North American cold wave was an extreme weather event that extended through the late winter months of the 2013–2014 winter season, and was also part of an unusually cold winter affecting parts of Canada and parts of the north-central and northeastern United States. The event occurred in early 2014 and was caused by a southward shift of the North Polar Vortex. Record-low temperatures also extended well into March.
The 2013–14 North American winter was one of the most significant for the United States, due in part to the breakdown of the polar vortex in November 2013, which allowed very cold air to travel down into the United States, leading to an extended period of very cold temperatures. The pattern continued mostly uninterrupted throughout the winter and numerous significant winter storms affected the Eastern United States, with the most notable one being a powerful winter storm that dumped ice and snow in the Southeastern United States and the Northeastern United States in mid-February. Most of the cold weather abated by the end of March, though a few winter storms did affect the Western United States towards the end of the winter.
The November 2014 North American cold wave was an extreme weather event that occurred across most of Canada and the contiguous United States, including parts of the Western United States up to western California. One of the first events of the winter, the cold wave was caused by the northward movement of an extremely powerful bomb cyclone associated with Typhoon Nuri's remnant, which shifted the jet stream far northward, creating an omega block pattern. This allowed a piece of the polar vortex to advance southward into the Central and Eastern United States, bringing record-cold temperatures to much of the region. In contrast, Alaska experienced above-average temperatures.
The 2014–15 North American winter was frigid and prolifically wintry, especially across the eastern half of North America in the months of January–March. The season began early, with many places in North America experiencing their first wintry weather during mid-November. A period of below-average temperatures affected much of the contiguous United States, and several records were broken. An early trace of snowfall was recorded in Arkansas. There were greater accumulations of snow across parts of Oklahoma as well. A quasi-permanent phenomenon referred to as the polar vortex may have been partly responsible for the cold weather. Temperatures in much of the United States dropped 15 to 35 °F below average by November 19, following a southward "dip" of the polar vortex into the eastern two-thirds of the country. The effects of this dip were widespread, bringing about temperatures as low as 28 °F (−2 °C) in Pensacola, Florida. Following a significant snowstorm there, Buffalo, New York received several feet of snow from November 17–21. In addition, significant winter weather occurred throughout the season, including a major blizzard that struck the Northeastern United States at the end of January, another blizzard that affected much of the Northern United States days later in early February, and several significant snow events paired with very frigid temperatures for much of February.
The 2015–16 North American winter was not as frigid across North America and the United States as compared to the 2013–14 and 2014–15 winters. This was mainly due to a strong El Niño, which caused generally warmer-than-average conditions. However, despite the warmth, significant weather systems still occurred, including a snowstorm and flash flooding in Texas at the end of December and a large tornado outbreak at the end of February. The main event of the winter season, by far and large, was when a crippling and historic blizzard struck the Northeastern United States in late January, dumping up to 3 feet of snow in and around the metropolitan areas. Several other smaller snow events affected the Northeast as well, but for the most part the heaviest snowstorms and ice stayed out further west, such as a severe blizzard in western Texas in late December, and a major late-season snowstorm in Colorado in mid-April.
The February 2015 North American cold wave was an extreme weather event that affected most of Canada and the eastern half of the United States. Following an earlier cold wave in the winter, the period of below-average temperatures contributed to an already unusually cold winter for the Eastern U.S. Several places broke their records for their coldest February on record, while some areas came very close. The cause of the cold wave was due to the polar vortex advancing southward into the eastern parts of the U.S, and even making it as far south as the Southeast, where large snow falls are rare. By the beginning of March, although the pattern did continue for the first week, it abated and retreated near the official end of the winter.
The 2017–18 North American winter saw weather patterns across North America that were very active, erratic, and protracted, especially near the end of the season, resulting in widespread snow and cold across the continent during the winter. Significant events included rare snowfall in the South, an outbreak of frigid temperatures that affected the United States during the final week of 2017 and early weeks of January, and a series of strong nor'easters that affected the Northeastern United States during the month of March. In addition, flooding also took place during the month of February in the Central United States. Finally the winter came to a conclusion with a powerful storm system that caused a tornado outbreak and blizzard in mid-April. The most intense event, however, was an extremely powerful cyclonic blizzard that impacted the Northeastern United States in the first week of 2018. Similar to the previous winter, a La Niña was expected to influence the winter weather across North America.
The December 2017–January 2018 North American cold wave was an extreme weather event in North America in which record low temperatures gripped much of the Central, Eastern United States, and parts of Central and Eastern Canada. Starting in late December as a result of the southward shift of the polar vortex, extremely cold conditions froze the eastern United States in the last few days of 2017 as well as into the new year. Following a brief respite in mid-January, cold temperatures swung back into the eastern U.S. shortly afterwards. The cold wave finally dissolved by around January 19, as near-average temperatures returned.
In late January 2019, a severe cold wave caused by a weakened jet stream around the Arctic polar vortex hit the Midwestern United States and Eastern Canada, killing at least 22 people. It came after a winter storm brought up to 13 inches (33 cm) of snow in some regions from January 27–29, and brought the coldest temperatures in over 20 years to most locations in the affected region, including some all-time record lows. In early February, a concentration of Arctic air colloquially referred to as the "polar vortex" moved west, and became locked over Western Canada and the Western United States. As a result, February 2019 was among the coldest and snowiest on record in these regions. In early March, the cold once again shifted east, breaking records in many areas. In mid-March, the cold wave finally retreated, but combined with above-average temperatures, precipitation, and a deep snowpack, widespread flooding ensued in the Central US.
The 2019–20 North American winter was unusually warm for many parts of the United States; in many areas, neutral ENSO conditions controlled the weather patterns, resulting in strong El Niño like conditions and the sixth-warmest winter on record, and many areas in the Northeastern United States saw one of the least snowy winters in years. In fact, Baltimore and Islip saw no snow in February for the first time. Some notable events still occurred, such as a powerful blizzard that impacted the Western United States in late November, a series of cold shots in January and February, a snowstorm within the Texas Panhandle and a late-season blizzard in the High Plains.
The February 2021 North American cold wave was an extreme weather event that brought record low temperatures to a significant portion of Canada, the United States and parts of northern Mexico during the first two-thirds of February 2021. The cold was caused by a southern migration of the polar vortex, likely caused by a sudden stratospheric warming event that occurred the prior month. Temperatures fell as much as 25–50 °F below average as far south as the Gulf Coast. Severe winter storms also were associated with the bitter cold, which allowed for heavy snowfall and ice accumulations to places as far south as Houston, Texas, and contributing to one of the snowiest winters ever in some areas in the Deep South.
The 2021–22 North American winter was not as significant and record-breaking as the previous winter season. Despite this, several notable and significant events still occurred, including two separate record-breaking tornado outbreaks in mid-December, a significant winter storm in the South in mid-January, a powerful blizzard that impacted the Northeast coast at the end of January and a wide-ranging, significant winter storm that affected most of the eastern half of the country in early February. Additional significant events included a late-season winter storm in March that affected the Appalachian Mountains, and a major blizzard that affected North and South Dakota in mid-April. Additionally, a very late out-of-season snowstorm struck the Rocky Mountains in late May. During the season, four storms have been ranked on the Regional Snowfall Index (RSI), although none attained the “Major” category. Similar to the previous winter, a developing La Niña was expected to influence weather patterns across the continent.
