2020–21 North American winter

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 (2021 USD). The season featured 6 storms ranking on the Regional Snowfall Index scale (RSI), with 4 storms ranking 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.

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.

Much of the country saw some form of winter weather and often significant impacts as a result, reflected by the numerous amount of 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 3 ft (0.91 m) of snow was reported across a swath in the interior Northeast, and the system caused 7 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 7 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 $27.1 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.