Storms in the Midwest generally develop in the Rocky Mountains and combine with cold air from Canada and moist air from the Gulf of Mexico or Pacific Ocean. The movement of these systems can lead to snow or other winter precipitation and extremely cold temperatures. Lift is responsible for bringing moisture from the air into the freezing temperatures within the clouds above to cause snow and ice. As this frozen moisture becomes too heavy to stay in the clouds, it falls to the ground and is affected by the ground temperatures below, which determines the precipitation we receive.
When temperatures drop below normal and winter storms bring precipitation, staying safe and warm can be difficult. Extremely cold temperatures and brisk winds can lead to life-threatening situations, while snowy or icy roads can make transportation treacherous.
Freezing Rain – Temperatures in the clouds range from 34-36 degrees, which keeps the moisture from freezing as it falls. However, ground temperatures ranging from 30-33 degrees means that the rain freezes to surfaces like trees, cars, roads and utilities as it reaches the surface. Even a small accumulation of this ice can cause a significantly hazardous situation.
Sleet – Cloud temperatures range from 32-34 degrees, but the temperature of the air falls between 30-31 degrees. This causes the rain pellets to freeze as they fall. Since they are already frozen before reaching the ground, these pellets do not stick to objects on the ground, but they do accumulate like snowfall and can be hazardous to motorists.
Snow – Cloud temperatures are below freezing, which causes snow to form, and continued temperatures in the surrounding air range from 30-31 degrees, which keeps the snow from melting as it falls.
- Flurries – light snow that falls in short durations. The result is a light dusting or no accumulation.
- Snow Showers – snow falls in varying intensities for brief periods of time. Accumulations will depend on the intensity and duration of the storm.
- Blowing Snow – wind-driven snow (either falling from the clouds or loose snow already on the ground) reduces visibility and causes hazardous driving conditions.
- Blizzard – winds of at least 35 mph blows falling snow into large accumulation areas and reduces visibility to near zero. Blizzard conditions are extremely hazardous due to reduced visibility and cold temperatures.
Wind Chill - Wind causes the effect of cold temperatures on the body (PDF) to have an even greater impact. As the wind increases, heat is carried away from the body at an accelerated rate, which further lowers body temperature.