Frost dates for Chicago, Illinois
In Chicago, half of springs have had their last frost by April 11 (and 1 spring in 10 still has one after April 27), and half of falls have had their first frost by October 31, leaving about 201 frost-free days in a typical year. Here is how sure those dates are, what they mean for planting, and where they come from.
Frost dates for
Chicago, Illinois
Last spring frost
April 11
Half of springs have their last frost by this date. For a safer bet, wait until April 27: only 1 spring in 10 has a frost after that.
First fall frost
October 31
Half of falls have their first frost by this date. In 1 fall in 10 it comes by October 20.
Growing season
201 days
Frost-free days in a typical year. 9 years in 10 get at least 181.
Hardiness zone
6a
2023 USDA map: the coldest night of winter averages −10°F to −5°F. It was 6a on the 2012 map too. ZIP codes within about 6 miles of the city's center: 19 in 6a and 11 in 6b.
Print a year planner for Chicago
Frost risk through the year
How sure are these dates?
A frost date is a probability, not a promise. NOAA worked out, from 30 years of nightly lows, how often the last spring frost and the first fall frost fall on each date. The middle column is the typical year. The outer columns are the early and late years that come about once a decade.
| Early year 1 in 10 | Typical year 1 in 2 | Late year 1 in 10 | |
|---|---|---|---|
| Last frost in spring | March 30 | April 11 | April 27 |
| First frost in fall | October 20 | October 31 | November 14 |
The frost-free season between them runs 201 days in a typical year. In 1 year in 10 it is 222 days or longer, and in 1 year in 10 it is 181 days or shorter.
- Hard freeze (28°F): typically last on April 1 and first on November 11. It is a harder freeze than the 32°F frost line, cold enough to damage many garden plants; how hardy a crop is decides whether it comes through. (The National Weather Service's own hard-freeze threshold varies from office to office.)
- Frost possible (36°F at the station): typically last on April 23 and first on October 21. On clear, still nights the ground can be several degrees colder than the thermometer, so frost can form on plants when the official reading is in the mid-30s.
In 8 springs out of 10, the last frost in Chicago comes between March 30 and April 27, a window of 28 days. That is about average for NOAA's stations (the typical window is 31 days).
Among Illinois's 170 NOAA stations with a frost every year, 78 percent have their typical last frost later than Chicago does.
Planting calendar for Chicago
These dates count from the typical last and first frosts, using the planting rules published by Colorado State University Extension (spring), Virginia Cooperative Extension (fall crops) and University of Minnesota Extension (garlic, where winters are hard). Weather in any one year can run early or late, so check the forecast before you plant tender crops.
| When | What to do | Why then |
|---|---|---|
| January | ||
| January 24 to February 21 | Broccoli and cabbage Start seeds indoors | 5 to 7 weeks before planting them out |
| February | ||
| February 7 to March 7 | Cauliflower Start seeds indoors | 5 to 7 weeks before planting out |
| February 21 to March 14 | Eggplant Start seeds indoors | 6 to 9 weeks before planting out |
| February 28 to March 14 | Peppers Start seeds indoors | 6 to 8 weeks before planting out |
| March | ||
| March 7 to 21 | Tomatoes Start seeds indoors | 5 to 7 weeks before planting out |
| March 14 to 28 | Peas, spinach, lettuce, radishes, onion sets, turnips Sow outdoors, as early as | hardy crops: 2 to 4 weeks before the typical last frost |
| March 14 to 28 | Broccoli and cabbage Plant out, as early as | hardy crops: 2 to 4 weeks before the typical last frost |
| March 28 to April 11 | Beets, carrots, potatoes, Swiss chard Plant outdoors, as early as | semi-hardy crops: up to 2 weeks before the typical last frost |
| March 28 to April 11 | Cauliflower Plant out, as early as | semi-hardy: up to 2 weeks before the typical last frost |
| April | ||
| April 11 | Snap beans, sweet corn, cucumbers, summer squash Sow outdoors around | tender crops: around the typical last frost date |
| April 25 | Tomatoes, peppers, eggplant Plant out from | very tender: 2 weeks or more after the typical last frost |
| April 25 | Melons, winter squash, pumpkins, lima beans Sow outdoors from | very tender: 2 weeks or more after the typical last frost |
| June | ||
| June 5 to 19 | Cabbage for fall Start seeds | set the plants out by July 24 |
| June 25 to July 9 | Broccoli for fall Start seeds | set the plants out by August 13 |
| August | ||
| August 4 | Snap beans for fall Last date to sow | 60 days to harvest, plus 2 weeks for slower fall growth, plus 2 weeks because frost kills it |
| August 8 | Carrots for fall Last date to sow | 70 days to harvest, plus 2 weeks for slower fall growth |
| August 9 | Cucumbers for fall Last date to sow | 55 days to harvest, plus 2 weeks for slower fall growth, plus 2 weeks because frost kills it |
| August 13 | Peas for fall Last date to sow | 65 days to harvest, plus 2 weeks for slower fall growth |
| August 14 | Summer squash for fall Last date to sow | 50 days to harvest, plus 2 weeks for slower fall growth, plus 2 weeks because frost kills it |
| August 18 | Leaf lettuce and beets for fall Last date to sow | 60 days to harvest, plus 2 weeks for slower fall growth |
| August 28 | Turnips and kohlrabi for fall Last date to sow | 50 days to harvest, plus 2 weeks for slower fall growth |
| September | ||
| September 7 | Spinach for fall Last date to sow | 40 days to harvest, plus 2 weeks for slower fall growth |
| September 17 | Radishes for fall Last date to sow | 30 days to harvest, plus 2 weeks for slower fall growth |
| October | ||
| October 20 | Tomatoes, peppers, squash, melons, cucumbers Watch the forecast from | in 1 fall in 10 the first frost comes by this date; pick tender crops before a frost |
| November | ||
| November 18 to 25 | Garlic Plant cloves | one or two weeks after the typical first hard freeze (28°F), our reading of the first killing frost |
Want more insurance? Shift every spring date 16 days later. That plans around April 27, the date after which only 1 spring in 10 has a frost.
For spring bulbs such as tulips and daffodils, plant once the soil has cooled to about 50 to 55°F and keep going until a couple of weeks before the ground freezes. Our guide to fall planting explains how to tell.
Where these numbers come from
These dates come from NOAA's weather station Chicago Midway Airport (station USW00014819), 5 miles from the center of Chicago. It sits at about the same elevation, 610 feet above sea level. NOAA rates this station's record as representative: at least 10 of the 30 years, with the gaps filled from nearby stations.
The same station also gives the frost dates for Cicero, Orland Park, Oak Lawn, Berwyn, Oak Park, Calumet City, Burbank and Oak Forest.
Our ZIP code lookup matches these 23 ZIP codes to the same station, so they get the same dates: 60130, 60141, 60153, 60154, 60155, 60301, 60302, 60304, 60305, 60402, 60501, 60513, 60526, 60534, 60546, 60620, 60623, 60629, 60632, 60636, 60638, 60644, 60804. Hardiness zones are worked out separately for each ZIP code.
Nearby places
- Naperville, Illinois: last frost around April 25, first frost around October 19 (25 miles away)
- Aurora, Illinois: last frost around April 28, first frost around October 13 (30 miles away)
- Joliet, Illinois: last frost around April 19, first frost around October 25 (35 miles away)
See frost dates across Illinois, or look up your own ZIP code for the station nearest you. Want the background? Read what a last frost date really means.