Winter Weather

Contents:
Definitions
Winter Weather Safety
Road Conditions
Winter Weather Statistics

Winter weather can impact all aspects of society, from travel to commerce to utilities, and it can be life threatening. Be prepared before winter weather hits to protect you and your family at home or on the road.

Winter Weather Definitions:

Winter Storm Watch - Conditions are favorable for hazardous winter weather conditions including heavy snow, blizzard conditions, or significant accumulations of freezing rain or sleet. These watches are usually issued 12 to 36 hours in advance of the event.

Winter Storm Warning - Hazardous winter weather conditions that pose a threat to life and/or property are occurring, imminent or likely. The generic term, winter storm warning, is used for a combination of two or more of the following winter weather events; heavy snow, freezing rain, sleet and strong winds. The following event-specific warnings are issued for a single weather hazard:

  • Blizzard Warning - Sustained winds or frequent gusts of 35 mph or greater, considerable falling and/or blowing snow reducing visibility frequently to 1/4 mile or less for a period of three hours or more. There are no temperature criteria in the definition of a blizzard but freezing temperatures and 35 mph winds will create single digit wind chills.
  • Heavy Snow Warning - Snowfall of 6 inches or more in 12 hours or less, or 8 inches or more in 24 hours or less.
  • Lake Effect Snow Warning - Lake effect snowfall of 6 inches or more in 12 hours or less, or 8 inches or more in 24 hours or less.
  • Ice Storm Warning - Accumulations of 1/4 inch or more of freezing rain.
  • Heavy Sleet Warning - Accumulations of 1/2 inch or more of sleet.

Winter Weather Advisory - Hazardous winter weather conditions are occurring, imminent or likely. Conditions will cause a significant inconvenience and if caution is not exercised, will result in a potential threat to life and/or property. The generic term, winter weather advisory, is used for a combination of two or more of the following events; snow, freezing rain or drizzle, sleet, blowing snow.

Wind Chill Warning - Extreme wind chills of -30oF or colder.

Wind Chill Advisory - Dangerous wind chills of -20oF to -30oF.

Wind Chill Temperature Chart
Wind Chill Chart
Click here for a Wind Chill Calculator

Winter Weather Safety

  • Illinois Emergency Management Agency
  • Ice Pack - promoting motorists' awareness of critical winter safety measures
    Ice Pack is comprised of the AAA-Chicago Motor Club; National Weather Service; Illinois State Police; Indiana State Police; American Red Cross; Illinois Department of Emergency Management; Indiana Toll Road; Illinois State Toll Highway Authority; Illinois Department of Transportation; and the Indiana Department of Transportation.
  • Tips on staying warm from the Chicago Department of Public Health
  • Winter Storms...the Deceptive Killers
    A Guide to Survival from the NWS and the American Red Cross
  • Indiana Winter Weather Guide
    pdf format

Road Conditions:

Winter Weather Statistics


MONTHLY SNOWFALL NORMALS FOR O'HARE (1971-2000)
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Annual
11.3
8.3
6.0
1.6
T
0
0
0
0
0.3
1.8
8.7
38.0
 
MONTHLY SNOWFALL NORMALS FOR ROCKFORD (1971-2000)
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Annual
10.3
7.9
5.6
1.4
T
0
0
0
0
0.1
2.6
10.8
38.7


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