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A Blue Norther, also known as a Texas Norther, is a fast moving cold front marked by a rapid drop in temperature, strong winds, and dark blue or "black" skies. The cold front originates from the north, hence the "norther", and can send temperatures plummeting by 20 or 30 degrees in merely minutes.
The Midwestern United States lacks natural geographic barriers to protect itself from the frigid winter air masses that originate in Canada and the arctic. Multiple times per year conditions will become favorable to push severe cold fronts as far south as Texas, bringing sleet and snow and causing the windchill to plunge into the teens. Depending on the time of year, high temperatures that immediately precede a Texas Norther can reach 85 °F (29°C) or even 90 °F (32°C) under bright sunlight in nearly-calm conditions before the cold front approaches.
However, most Blue Northers don't advance as far south as Mexico, and even the most severe examples typically reach their apex midway through Texas. For example, cities in North Texas, like Dallas, experience drastically more Blue Northers than cities along the Gulf of Mexico, like Houston. As a city is struck by a Blue Norther, its temperatures can be 30 to 50 degrees colder than neighboring cities that are only a few miles away that have not yet been struck. Blue Northers can be dangerous due to their volatile temperature swings which catch some people unprepared.
Blue Northers occur multiple times per year. They are usually recorded between the months of November and March, although they have been recorded less frequently in October and April as well. The Blue Norther phenomenon is especially common in November, when the last vestiges of autumn are still clinging to life. One of the most famous Blue Northers was the Great Blue Norther of November 11, 1911, which spawned multiple tornadoes and dropped temperatures 40 degrees in only 15 minutes and 67 degrees in 10 hours, a world record.
A blizzard is a severe snowstorm characterized by strong sustained winds and low visibility, lasting for a prolonged period of time—typically at least three or four hours. A ground blizzard is a weather condition where snow is not falling but loose snow on the ground is lifted and blown by strong winds. Blizzards can have an immense size and usually stretch to hundreds or thousands of kilometres.
Lake-effect snow is produced during cooler atmospheric conditions when a cold air mass moves across long expanses of warmer lake water. The lower layer of air, heated by the lake water, picks up water vapor from the lake and rises through colder air. The vapor then freezes and is deposited on the leeward (downwind) shores.
The desert climate or arid climate, is a dry climate sub-type in which there is a severe excess of evaporation over precipitation. The typically bald, rocky, or sandy surfaces in desert climates are dry and hold little moisture, quickly evaporating the already little rainfall they receive. Covering 14.2% of earth's land area, hot deserts are the second most common type of climate on earth after the polar climate.
On Saturday, November 11, 1911, a cold snap, known as the Great Blue Norther or 11/11/11, affected the Central United States. Many cities broke record highs, going into the 70s and 80s early that afternoon. By nightfall, cities were dealing with temperatures in the teens and single-digits on the Fahrenheit scale. This is the only day in many midwest cities' weather bureau jurisdictions where the record highs and lows were broken for the same day. Some cities experienced tornadoes on Saturday and a blizzard on Sunday. A blizzard even occurred within one hour after an F4 tornado hit Rock County, Wisconsin.
The 1991 Halloween blizzard was a powerful storm that caused a period of heavy snowfall and ice accumulation, which affected parts of the Upper Midwest of the United States, from October 31 to November 3, 1991. Over the last week of October 1991, a large storm system over the Atlantic Ocean blocked most of the weather patterns over the eastern half of the United States, and in turn, moisture from the Gulf of Mexico was funneled straight northward over the affected region. By the time the precipitation stopped falling, many cities in the eastern half of Minnesota and northwestern Wisconsin had witnessed record early-season snowfall accumulations, while parts of southern Minnesota and northern Iowa were crippled by a large ice storm. Arctic air that was pulled southward behind the storm had combined with the heavy snow pack to produce many record low temperatures. Between the blizzard and the ice storm, 22 people were killed and over 100 were injured.
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.
Minnesota has a humid continental climate, with hot summers and cold winters. Minnesota's location in the Upper Midwest allows it to experience some of the widest variety of weather in the United States, with each of the four seasons having its own distinct characteristics. The area near Lake Superior in the Minnesota Arrowhead region experiences weather unique from the rest of the state. The moderating effect of Lake Superior keeps the surrounding area relatively cooler in the summer and warmer in the winter, giving that region a smaller yearly temperature variation. On the Köppen climate classification, much of the southern third of Minnesota—roughly from the Twin Cities region southward—falls in the hot summer zone (Dfa), and the northern two-thirds of Minnesota falls in the warm summer zone (Dfb).
Tornadoes have been recorded on all continents except Antarctica. They are most common in the middle latitudes where conditions are often favorable for convective storm development. The United States has the most tornadoes of any country, as well as the strongest and most violent tornadoes. A large portion of these tornadoes form in an area of the central United States popularly known as Tornado Alley. Canada experiences the second most tornadoes. Ontario and the prairie provinces see the highest frequency. Other areas of the world that have frequent tornadoes include significant portions of Europe, South Africa, Philippines, Bangladesh, parts of Argentina, Uruguay, and southern and southeastern Brazil, northern Mexico, New Zealand, and far eastern Asia.
The Early Winter 2006 North American storm complex was a severe winter storm that occurred on November 26, 2006, and continued into December 1. It affected much of North America in some form, producing various kinds of severe weather including a major ice storm, blizzard conditions, high winds, extreme cold, a serial derecho and some tornadoes.
The climate of Houston is classified as a humid subtropical climate, with tropical influences. August normally ranks as the warmest month at 84.6 °F (29.2 °C) and January the coldest month at 53.1 °F (11.7 °C).
The climate of the north and central parts of the US state of Florida is humid subtropical. South Florida has a tropical climate. There is a defined rainy season from May through October when air mass thundershowers that build in the heat of the day drop heavy but brief summer rainfall.
Texas' weather varies widely, from arid in the west to humid in the east. The huge expanse of Texas encompasses several regions with distinctly different climates: Northern Plains, Trans-Pecos Region, Texas Hill Country, Piney Woods, and South Texas. Generally speaking, the part of Texas that lies to the east of Interstate 35 is subtropical, while the portion that lies to the west of Interstate 35 is arid desert.
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 the United States varies due to changes in latitude, and a range of geographic features, including mountains and deserts. Generally, on the mainland, the climate of the U.S. becomes warmer the further south one travels, and drier the further west, until one reaches the West Coast.
The Geography of Atlanta encompasses 132.4 square miles (342.9 km2), of which 131.7 square miles (341.1 km2) is land and 0.7 square miles (1.8 km2) is water. The city is situated among the foothills of the Appalachian Mountains, and at 1,050 feet (320 m) above mean sea level, Atlanta has the highest elevation among major cities east of the Mississippi River. Atlanta straddles the Eastern Continental Divide, such that rainwater that falls on the south and east side of the divide flows into the Atlantic Ocean, while rainwater on the north and west side of the divide flows into the Gulf of Mexico. Atlanta sits atop a ridge south of the Chattahoochee River, which is part of the ACF River Basin. Located at the far northwestern edge of the city, much of the river's natural habitat is preserved, in part by the Chattahoochee River National Recreation Area.
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-then-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 2010–11 North American winter was influenced by an ongoing La Niña, seeing winter storms and very cold temperatures affect a large portion of the Continental United States, even as far south as the Texas Panhandle. Notable events included a major blizzard that struck the Northeastern United States in late December with up to 2 feet (24 in) of snowfall and a significant tornado outbreak on New Year's Eve in the Southern United States. By far the most notable event was a historic blizzard that impacted areas from Oklahoma to Michigan in early February. The blizzard broke numerous snowfall records, and was one of the few winter storms to rank as a Category 5 on the Regional Snowfall Index. In addition, Oklahoma set a statewide low temperature record in February.
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 2018–19 North American winter was unusually cold within the Northern United States, with frigid temperatures being recorded within the middle of the season. Several notable events occurred, such as a rare snow in the Southeast in December, a strong cold wave and several major winter storms in the Midwest, and upper Northeast and much of Canada in late January and early February, record snowstorms in the Southwest in late February, deadly tornado outbreaks in the Southeast and a historic mid-April blizzard in the Midwest, but the most notable event of the winter was a record-breaking bomb cyclone that affected much of the Central United States and Canada in mid-March. Unlike previous winters, a developing weak El Niño was expected to influence weather patterns across North America. Overall, however, winter of 2018–19 was mild along the mid- and lower parts of the East Coast, the West Coast, and most of the southern Plains. Overall, the meteorological winter of 2018-19 became the wettest on record for the United States.
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 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.
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