An arctic blast is sweeping across the U.S. The National Weather Service predicts a bomb cyclone will hit Thursday into Friday.
What is a bomb cyclone?
According to the National Ocean Service, the term is used when a "midlatitude cyclone rapidly intensifies, dropping at least 24 millibars over 24 hours."
Millibars are how atmospheric pressure is measured.
"Storms, of course, always have lower atmospheric pressure, but in this case, the atmospheric pressure is lowering very quickly as the storm system intensifies," according to AccuWeather Chief Meteorologist Jon Porter.
In places like Denver, temperatures dropped about 40 degrees within an hour.
Bomb cyclones can have dangerous effects. According to The National Oceanic and Atmospheric Administration, it can cause high, intense winds that cause power outages.
Blizzard conditions with heavy blowing are also a major concern.
Some areas could also experience rainfall or snow that could cause river flooding.
It's forecasted this will be the coldest Christmas in decades for much of the country.