Ice jam flooding is a danger when snow and ice begin thawing. The science of winter weather When where, and how much cold air moves into the USA depends in large part on the position and strength of the polar vortex. Lake effect snow brings the Great Lakes region some of the USA's heaviest snow. Northeasters are the big storms that can dump snow on the East Coast states. Alberta Clippers form over Alberta, Canada and race southeastward across the USA with snow, often light, and often drag cold air south.
Clouds keep winter nights warmer than they are on clear nights.
Winter weather records Each USA state's low temperature record. The Snow Booklet has facts and figures about snow, including the USA's snowiest large city. Every year dozens of people around the globe are killed on mountains and in the backcountry by avalanches. The links below take you to more detailed information on avalanches. The Northwest Weather and Avalanche Center has avalanche forecasts and information for Washington and Oregon.