As millions of Americans hunker down for the winter storm, 19 states and Washington, D.C., have declared states of emergency.

In a typical summertime thunderstorm, warm, moist air rises rapidly into the atmosphere, where it hardens into ice crystals, ...

In the Northeast, forecasts have called for 12 to 18 inches, though totals will vary locally and may be lower along the immediate coast. Mr. Lamers noted the potential for a “slowly pivoting snow band ...

The temperature has a huge impact on what kind of snowflakes fall, as well as how many inches of snow piles up.

The winter storm is here and two-thirds of the US population is facing this extreme cold. More than half of all Americas will experience subzero wind chills over the next 3 days.