Heavy Snow and Strong Winds Across the North-Central U.S.; Heavy Rain and Flash Flooding in American Samoa and Puerto Rico

Areas of moderate to heavy snow and gusty to high winds are expected across the Northern Plains, Upper Midwest and Great Lakes into Friday. Several inches of snow accumulation is expected. Heavy rain will bring an isolated flash flood threat to Puerto Rico and flash flooding along with mudslides to American Samoa today. Read More >

This page houses climatological snowfall data for the NWS Chicago County Warning Area (CWA), a 23 county area that includes a large portion of northern Illinois and northwest Indiana. Much of the information is for two official climate sites, Chicago and Rockford, as these locations have longtime, quality-controlled climate data.

Besides climatology, this page can serve to help with snowfall risk assessment in terms of time of year, frequency, and magnitude. For more on specific snow events of the past, please visit our Past Events Page, WPC Storm Summaries, and the NCEI Storm Events Database.

Courtesy of Laurie Stahl in Antioch, IL

Chicago
Rockford
County Warning Area
Archetypes
Links

Chicago

Normals for Chicago O'Hare are from 1991-2020 unless otherwise noted. Records for multiple official Chicago sites are from 1886-present.

Normal and Record Snowfall

For seasonal and monthly normals and records, please visit our Local Climate Page.

Trace or More of Snow

Normal First Date:	October 31	Normal Last Date:	April 14
Earliest First:	September 25, 1928	Earliest Last:	March 4, 2012
	September 25, 1942
Latest First:	December 5, 1999	Latest Last:	May 25, 1924

Measurable (0.1 Inches or More)

Normal First Date:	November 18	Normal Last Date:	April 2
Earliest First:	October 12, 2006	Earliest Last:	February 28, 1994
Latest First:	December 28, 2021	Latest Last:	May 11, 1966

One Inch or More

Normal First Date:	December 7	Normal Last Date:	March 20
Earliest First:	October 19, 1989	Earliest Last:	January 18, 1927
Latest First:	January 25, 2013	Latest Last:	May 3-4, 1907
		Latest calendar day 1+": May 1, 1940

Temporal Climatology of Days with >= 0.1 in. of Snow			Temporal Climatology of Days with >= 1.0 in. of Snow

Average Number of 1-Day Snow Totals a Season			Average Number of 2-Day Snow Totals a Season

Rockford

Normals for Rockford are from 1991-2020 unless otherwise noted. Records for multiple official Rockford sites are from 1906-present, though some years are missing.

Normal and Record Snowfall

For seasonal and monthly normals and records, please visit our Local Climate Page.

Trace or More of Snow

Normal First Date:	October 31	Normal Last Date:	April 11
Earliest First:	September 25, 1928	Earliest Last:	March 5, 2012
Latest First:	December 19, 1999	Latest Last:	May 24, 1925

Measurable (0.1 Inches or More)

Normal First Date:	November 20	Normal Last Date:	April 1
Earliest First:	October 12, 1909	Earliest Last:	February 6, 1911
Latest First:	January 7, 1940	Latest Last:	May 11, 1966

One Inch or More

Normal First Date:	December 4	Normal Last Date:	March 18
Earliest First:	October 23, 1917	Earliest Last:	February 2, 1968
	October 23, 1929
Latest First:	February 7, 1921	Latest Last:	May 11, 1966

Temporal Climatology of Days with >= 0.1 in. of Snow			Temporal Climatology of Days with >= 1.0 in. of Snow

Average Number of 1-Day Snow Totals a Season			Average Number of 2-Day Snow Totals a Season

Northern Illinois and Northwest Indiana

Average Annual U.S. Snowfall			Average Annual Great Lakes Snowfall

These maps were created by Kaye LaFond of NOAA GLERL and Zoe Zaloudek of the Midwestern Regional Climate Center.

The below maps are courtesy of the NOAA Midwestern Regional Climate Center's Snow Climatology Tool and are averages for a winter season.

Average Number of 1-Day Snow Totals >= 1" Per Season	Average Number of 2-Day Snow Totals >= 1" Per Season

Average Number of 1-Day Snow Totals >= 3" Per Season	Average Number of 2-Day Snow Totals >= 3" Per Season

Average Number of 1-Day Snow Totals >= 6" Per Season	Average Number of 2-Day Snow Totals >= 6" Per Season

Archetypes

These composite maps show the general surface low tracks most frequently associated with heavy snow totals (6+ inches) in the NWS Chicago CWA. These include a majority of the heavy snow events but not all of them. These images can help with applying the conceptual model and appropriately interpreting forecast guidance.