Chicago, IL Frost Dates: Last Spring and First Fall Frost

Frost leaves Chicago on April 10 and comes back on November 5 when the odds are even, a window of 208 days for tender plants.

Put April 25 and October 24 on the calendar as well. A spring freeze after the first of them, or a fall freeze before the second, happens in only one year out of ten, so those dates cover nine years in ten. Against the 100-city median of 229 days, Chicago has 21 days less room before frost returns.

The numbers belong to Chicago Northerly Is, NOAA station USC00111550, which sits 4.1 miles east of the Census Bureau's internal point for Chicago at an elevation of about 580 feet.

Chicago's last spring frost, by chance

One year in ten has a freeze on or after April 25. In nine years out of ten there is still a freeze on or after March 29, and half of years see one on or after April 10.

From the 90% date to the 10% date is 27 days, a short span next to most cities here, which makes the spring calendar in Chicago steadier than average.

First fall frost in Chicago

Expect the first freeze of fall by November 5 in a typical year. One year in ten brings it by October 24, and nine in ten have had it by November 20.

The early and late fall dates are only 27 days apart, a narrow band next to most cities here, so the first freeze keeps close to its schedule in Chicago.

How long is the frost-free season in Chicago?

The season is somewhat shorter than the middle of these pages, so a seed packet's days to maturity deserve a second look. There is little difference between a typical season (208 days) and a short one (187 days) in Chicago: 21 days, less than in most of the cities covered here.

The season lengths come from NOAA's simulated years, not from subtracting one typical date from the other, so the two will not match to the day. At Chicago Northerly Is a night at or below 32°F turns up in 100% of years, which means these dates apply every winter.

Hard freeze dates for Chicago

A hard freeze follows the first frost quickly in Chicago: the typical 28°F night arrives on November 15 in fall, only 10 days after the first 32°F one on November 5, and in spring the last one comes on April 1, 9 days before the last 32°F frost. Tender plants get little warning here. One spring in ten still has a 28°F night on or after April 14, and one fall in ten sees the first by November 2.

What this means for planting in Chicago

The University of New Hampshire Extension sheet times each crop from the last frost. For Chicago's typical date, April 10, that means cabbage on March 13, lettuce from March 13 to March 20, seed potatoes from March 27 to April 3, and, once the frost is behind you, peppers on April 24 and beans on or after April 10. Peas have no frost-based date in the University of New Hampshire Extension sheet: they go in as soon as the soil thaws.

From the late date, April 25, every tender crop moves back 15 days; that buys protection against a spring only one year in ten brings.

Fall crops are counted back from the first frost, using NC State Extension's days to harvest plus University of Georgia Extension's harvest allowance of 18 days. In Chicago only 32 of the 34 crops in the fall planner have a last planting day in July or later, and the other 2 would have to go in before then, in spring or early summer. The slowest crop that still fits is lima/pole beans, at 113 days, and it has to be planted by July 3 to beat the early date.

Worked example: tomatoes in Chicago

Suppose you want tomatoes in Chicago. University of New Hampshire Extension says to set transplants out one to two weeks after the last frost. Counting from the typical date, April 10, the window runs from April 17 to April 24. Counting from the late date, April 25, it moves to May 2 through May 9, which is 15 days later.

Indoors, tomato seeds go in six to eight weeks ahead of set-out; from the first day of the late window that is March 7 to March 21.

From the last set-out day to the early first frost on October 24 is 168 days. NC State Extension gives 75 to 85 days, and the longer figure still fits with 83 days to spare.

Where Chicago's numbers are measured

The nearest usable station stands 4.1 miles east of Chicago's internal point, near the city but not in it.

NOAA lists it at about 580 feet, higher than 40 and lower than 59 of the 100 stations in this set. Its completeness flag is R, which NOAA uses for a representative record.

Because the Census file has no elevation for Chicago, we cannot say how far your yard is above or below this station. When yours is clearly higher or lower, open the nearby stations in the frost dates tool and favor the colder one.

Chicago compared with nearby cities

Of the cities on these pages, Milwaukee, WI is closest to Chicago at 86 miles, with two more farther out; none is a close neighbor.

• Milwaukee, WI (86 miles, north): spring frost lingers 16 days longer than in Chicago, and it has 35 days less without frost. Its typical dates are April 26 and October 18, with 173 days frost-free.
• Madison, WI lies 124 miles north-west of Chicago. Typical last frost May 1, first frost October 9, 161 days between; spring frost lingers 21 days longer than in Chicago, and it has 47 days less without frost.
• Fort Wayne, IN (141 miles, east): its last frost comes 14 days after Chicago's, and the season runs 30 days shorter. Its typical dates are April 24 and October 21, with 178 days frost-free.

Take these dates further

Open the frost dates tool with this station already chosen to see the whole ladder of probability dates, or try the nearby stations in the same list. The spring planting planner and the fall planting planner turn the same dates into a full crop list, and the hardiness zone lookup tells you which perennials will survive the winter.

All the cities on these pages are listed by state on the city frost dates index.

For Illinois, the state planting pages copy the Extension calendar (University of Illinois Extension) crop by crop and region by region: tomatoes in Illinois, peppers in Illinois, cucumbers in Illinois, summer squash in Illinois, green beans in Illinois, potatoes in Illinois. Set those windows beside the frost dates above.

Where these numbers come from

The frost and freeze dates are NOAA's U.S. Climate Normals for 1991–2020 (doi:10.25921/4ek7-fk11), copied from the station's own record without adjustment; NOAA's documentation defines each probability. The city and its internal point come from the Census Bureau's 2024 Gazetteer of places, and the ranking by size from the Census Bureau's Vintage 2024 city and town population estimates, which put Chicago at 2,721,308 people.

Planting dates here are those rules from University of New Hampshire Extension, NC State Extension and University of Georgia Extension, applied to this station's frost dates and nothing else. The methodology page explains how each figure is checked.

NOAA's dates say how often frost has come, not when it will. Check the forecast before planting and keep a cover on hand.