The 2020–21 North American winter was the most significant winter season to affect North America in several years, and the costliest on record, with a damage total of at least $33.35 billion dollars (2021 USD). The season featured historic arctic blasts and multiple winter storms across much of the country. The Weather Prediction Center (WPC) tracked a total of 19 total significant winter storms, while six storms were ranked on the Regional Snowfall Index scale (RSI), four of which ranked as at least a Category 3. Most of the winter's damage and fatalities occurred due to a historic and major cold wave in mid-February. Several other significant events occurred, including a crippling early-season ice storm in the Southern Plains, a powerful nor'easter in mid-December, another major nor'easter in early February, two major and widespread winter storms in mid-February, and a major blizzard in the Rocky Mountains in mid-March. The winter-related events were responsible for at least 358 fatalities, making it the deadliest season since 1992–93. A La Niña pattern influenced much of the winter in North America.
Much of the country saw some form of winter weather and often significant impacts as a result, reflected by the numerous storms rated on the RSI. In mid-December, a significant Category 2 nor'easter affected much of the Northeastern United States with heavy snow and ice. Over of snow was reported across a swath in the interior Northeast, and the system caused seven fatalities. In early February, a major Category 3 nor'easter, which started out as a winter storm on the West Coast, impacted an even larger area with heavy snow, also causing seven fatalities. In mid-February, a series of two major Category 3 winter storms brought a swath of widespread snow and ice from the Pacific Northwest, through the Deep South, and to the Northeast. In total, the two winter storms resulted in at least $33.3 billion in damage, nearly 14 million power outages, and a total of 319 fatalities. In mid-March, a historic Category 3 blizzard unfolded in the Rocky Mountains, with Denver and Cheyenne seeing one of their largest March snowstorms on record.
While there is no well-agreed-upon date used to indicate the start of winter in the Northern Hemisphere, there are two definitions of winter which may be used. Based on the astronomical definition, winter began at the winter solstice on December 21, 2020 and ended at the spring equinox on March 20, 2021. Based on the meteorological definition, the first day of winter was on December 1 and the last day was February 28. However, as illustrated by the late October ice storm and the mid-April nor'easter, winter storms occasionally occur outside of these limits. Since both definitions of winter span the start of the calendar year, it is possible to have a winter storm in two different years, as shown by the New Year's winter storm this season.
Seasonal forecasts
On October 15, 2020, the National Oceanic and Atmospheric Administration's Climate Prediction Center released its U.S. Winter Outlook. The temperature and precipitation outlooks reflected the likelihood of a La Niña pattern developing during most of the winter. The forecast called for warmer than average temperatures across much of the southern and southwestern United States, as well as the East Coast, with cooler than average temperatures in the far northwestern United States. Near-average temperatures were expected in the Midwest. The forecast also called for drier than average conditions across almost all of the southeastern and southwestern United States, and wetter than average conditions in much of the northern tier and Midwest, with near-average precipitation in the Northeast and parts of the Midwest.
On November 30, 2020, Environment Canada released its winter outlook for December, January and February as part of their monthly climate outlooks. The agency predicted near to above average temperatures across most of Canada; particularly in the southern regions of the nation, such as southern British Columbia, southern Ontario, Quebec, and especially Atlantic Canada. Below average temperatures were expected to develop in the northern regions of the providences, as well in the northern Canadian Prairies due to the polar vortex and La Nina. Above average precipitation was forecasted to occur in British Columbia, southern Quebec, and quite evidently Atlantic Canada as well.
Seasonal summary
Winter weather events began in late October in North America, with a crippling and devastating ice storm in the Southern Plains, which later merged with the remnants of Hurricane Zeta and produced more snow in New England. November was generally quiet in terms of winter weather, with only a few minor snow events in the Midwest. Late in the month however, a storm system moved through the Ohio Valley bringing over of snow to Cleveland, and over of snow to areas just south of Lake Erie in northeast Ohio. December began with a nor'easter that impacted parts of New England with heavy snow. Later in the month, a powerful nor'easter brought heavy and impactful snow to widespread areas of the Northeastern United States and southern Canada. Major cities such as New York City, Pittsburgh, and Boston saw over of snow from the system. Areas farther inland saw as much as of snow. Around Christmas week, a powerful blizzard impacted the Midwestern United States and Canada, which also caused severe storms in the Southeast. A powerful extratropical cyclone in the Bering Sea late in the month reached winds of over and a minimum central pressure of west of Alaska. It later moved on to hit Alaska, after only slightly weakening, causing high surf and gusty winds in the Aleutian Islands.
January and the new year began with a storm system moving from the Gulf of Mexico to the Northeast on New Year's Eve and New Year's Day. It produced a swath of wintry weather extending over 2,000 miles, and the system also produced up to of snow and over of ice in some areas. Later in the month, a storm originating in the Rocky Mountains produced a swath of wintry weather from New Mexico through Alabama, including areas such as Lubbock, Austin, Metro Houston, and Shreveport, some of which saw over 6 inches of snow accumulation. Towards the middle of the month, a blizzard impacted the Midwest and the interior Northeast, producing heavy snow and extremely gusty winds behind the system. During the last full week of January, a storm with winter weather spanning over 1,500 miles produced snowfall and mixed precipitation from the Midwest to the Northeast, as well as causing severe weather in the Southeast. It was shortly followed by a cold wave in the Northeast, in which wind chills dropped to as low as and that prompted an area of wind chill advisories. At the end of the month, a storm complex and atmospheric river event began to unfold in the Western United States, with snowfall totals as high as and rainfall totals over a foot in many areas, causing widespread flooding and mudslides. The system later became a nor'easter bringing heavy and impactful snow to both coastal and interior areas of the Northeast, with both the Boston and New York City metropolitan areas seeing of snow, in addition to causing over $1.8 billion in damages.
February began with a winter storm that moved through the Great Plains and Midwest, with heavy snow and blizzard-like conditions sparking a 40-vehicle pileup on Interstate 80 eastbound in Iowa, causing several serious injuries. It was followed just a few days later by a fast-moving nor'easter that brought moderate snowfall to the I-95 corridor on the day of Super Bowl LV. Then, a series of major winter storms blasted through the Western, Southern, and Eastern United States bringing heavy snow and ice. The first two storms were both major ice storms, with the first ice storm resulting in 12 fatalities and the second causing up to of freezing rain accretion. The next two storms were both Category 3 winter storms on the Regional Snowfall Index scale, with the first of the storms causing at least 237 fatalities and about $22.5 billion in damage, making it the costliest winter storm on record. The second storm caused at least 29 fatalities and resulted in over $2 billion in damage. The last two storms also resulted in a major power crisis in Texas. In total, the four back-to-back storms resulted in tens of billions of dollars in damage, over 250 fatalities, at least 14 million power outages, and a crisis in the Deep South. Simultaneous to the barrage of winter storms was a historic, long-lived outbreak of Arctic air in the Central United States. Temperatures 30-50 °F (17-28 °C) below average for prolonged periods from February 12–19 resulted in the entire month of February being significantly below average. The month ended with a minor snowstorm that affected areas such as Denver in the Rocky Mountains.
March began with a cold wave and windstorm in New England, which prompted wind chill warnings in four states and resulted in over 165,000 power outages. Later in the month, a historic and major blizzard impacted the Rocky Mountains with feet of snow, nearly breaking numerous all-time records, especially in the Denver and Cheyenne areas. It was also responsible for a major late-season snowstorm in the Midwest as well. It was shortly followed by another severe blizzard in the Southern Plains, resulting in near-zero visibility, major highways being stopped for hours, and several injuries. In mid-April, a fairly strong nor'easter moved up the East Coast, resulting in heavy snowfall accumulations in interior New England, as well as widespread lower totals closer to the coast.
Events There were several winter weather events during the 2020–21 North American winter. Significant events include cold waves, snowstorms, ice storms, blizzards, and other notable events outside the conventional limits of winter.
Late October ice storm On October 27, a winter storm, unofficially named Winter Storm Billy by The Weather Channel, delivered heavy snow to Colorado, New Mexico, Western Texas, and Kansas, while a crippling ice storm hit Central Oklahoma, and Western North Texas including Oklahoma City. Ice accumulations were as high as in areas of the Oklahoma City metropolitan area. The ice storm resulted in widespread tree damage and over 400,000 customers being put without power, 40,000 of whom remained out of power ten days later. It was one of the worst ice storms in Oklahoma City history, and the largest power outage in OG&E history.Thousands of Oklahomans still without power, OG&E says outage is largest in company history, KFOR, November 1, 2020 The Storm led to the United States's most extensive October snow cover since 1967. The ice storm is estimated to have caused over $125 million (2020 USD) in damage. There were also two deaths: one in Kansas and one in Texas.
Post-Tropical Cyclone Zeta
The extratropical remnants of Hurricane Zeta combined with the previous winter storm to produce two separate snow events across parts of southern New England and upstate New York on October 29–30. The highest amount of accumulation was , which was recorded in Grafton, Massachusetts. This early-season snowstorm resulted in some downed tree branches in the region. The snowstorm also caused slippery road surfaces, leading to numerous crashes, some serious, in the state of Massachusetts. High wind in New York City caused a crane to damage the Steinway Building.
The cold front associated with Zeta dropped temperatures on the morning of October 31 to in Albany, New York, just one degree shy of the record. This is well below the typical low temperature of . Highs that day struggled to get into the 40s. Parts of New Jersey get as low as after Zeta dropped snow in the northern portion of the state, accumulating to in High Point State Park.
Late November storm complex