Oh, the weather outside is – snow. And lots of it if you live in the Buffalo, N.Y., area.
As part of this historic snowstorm, Buffalo was hit with at least five feet of lake-effect snow in 24 hours that resulted in eight deaths, road closures, and countless cancellations. Gov. Andrew Cuomo (D) declared a state of emergency for 10 counties, including Erie County, which has borne the brunt of the storm.
By Thursday afternoon, close to two feet of new snow had come down.
But just what is lake-effect snow? Here's what you need to know:
Typically occurring between November and February, lake-effect snow occurs when cooler air moves over a warmer body of water. In the case of Buffalo, that body of water would be Lake Erie.
The cooler air takes up water, freezes it, and then drops it in the form of snow on the side of the lake toward which the wind is blowing. This can happen in Midwestern states like Michigan and Indiana as well as places like Buffalo, according to NBC News meteorologist Domenica Davis.
Water retains heat longer than air, and water holds on to warmth accumulated throughout the summer months. After summer, therefore, the temperature of water is typically warmer than that of air. According to Joseph Stromberg, writing in Vox, the temperature difference between the water and air needs to be significant, about 20 to 30 degrees F., for lake-effect snow to happen. Moreover, he writes, the air needs to travel a sufficient distance across the water to attract the requisite amount of moisture.
The clouds that form produce snow when they hit land. This happens because the temperature of land is colder than water, which causes the temperature of the cloud to drop. And land's higher elevation means that the clouds can no longer hold on to so much moisture. So they release lots of it in the form of snow, which can happen rapidly.
However, once a body of water freezes over in the winter, the source of moisture stops and lake-effect snow is effectively halted.
Outside of New York, other major affected areas this week include Michigan and Indiana, where low temperatures and heavy snowfall have triggered accidents, injuries, and road closures, The Weather Channel reports.