The January 31 – February 3, 2021 nor'easter, also known as the 2021 Groundhog Day nor'easter, was a powerful, severe, and erratic nor'easter that impacted much of the Northeastern United States and Eastern Canada from February 1–3 with heavy snowfall, blizzard conditions, strong gusty winds, storm surge, and coastal flooding. The storm first developed as an extratropical cyclone off the West Coast of the United States on January 25, with the storm sending a powerful atmospheric river into West Coast states such as California, where very heavy rainfall, snowfall, and strong wind gusts were recorded, causing several hundred thousand power outages and numerous mudslides. The system moved ashore several days later, moving into the Midwest and dropping several inches of snow across the region. On February 1, the system developed into a nor'easter off the coast of the Northeastern U.S., bringing prolific amounts of snowfall to the region. Large metropolitan areas such as Boston and New York City saw as much as 18–24 inches (46–61 cm) of snow accumulations from January 31 to February 2, making it the worst snowstorm to affect the megalopolis since the January 2016 blizzard. It was given the unofficial name Winter Storm Orlena by The Weather Channel.

A nor'easter, is a large-scale extratropical cyclone in the western North Atlantic Ocean. The name derives from the direction of the winds that blow from the northeast. The term is commonly used in the winter in New England and Atlantic Canada.