Chicago, Illinois: planting zone & frost dates
Chicago is in USDA plant hardiness zone 6a, where the average coldest winter night reaches -10 to -5°F (-23.3 to -20.6°C). The typical last spring frost is around Apr 17 and the first fall frost around Nov 1.
Frost dates
| Probability | Last spring frost (32°F) | First fall frost (32°F) |
|---|---|---|
| Safer (10% risk) | Apr 25 | Oct 24 |
| Typical planning date (30% risk) | Apr 17 | Nov 1 |
| Median (50%) | Apr 10 | Nov 5 |
How to read this: after the spring "10% risk" date, a 32°F frost happens in only about 1 year in 10. In fall, the "10% risk" date is the early end — a frost before it happens about 1 year in 10.
Frost data comes from NOAA station CHICAGO NORTHERLY IS, IL (USC00111550), 4.1 mi (6.6 km) from the city center and 10 ft lower than the city center (-3 m). Record used for the 1991–2020 normals: 15 years.
Why your yard may differ from the station: microclimates.
Hardiness zone across Chicago
Chicago spans more than one half-zone. Share of the city's land area by zone (via its 55 ZIP codes): 6a (89%), 6b (11%). The headline zone is the one covering the most land. Look up your ZIP for your exact zone.
ZIP codes in Chicago and their zones
| ZIP | Zone | Share of city land |
|---|---|---|
| 60617 | 6a | 6.0% |
| 60628 | 6a | 4.8% |
| 60018 | 6a | 3.5% |
| 60633 | 6a | 3.5% |
| 60609 | 6a | 3.4% |
| 60632 | 6a | 3.3% |
| 60643 | 6a | 3.2% |
| 60634 | 6a | 3.1% |
| 60620 | 6a | 3.0% |
| 60629 | 6a | 3.0% |
| 60608 | 6a | 2.7% |
| 60619 | 6a | 2.7% |
| 60638 | 6a | 2.6% |
| 60623 | 6a | 2.4% |
| 60618 | 6a | 2.2% |
| 60639 | 6a | 2.2% |
| 60630 | 6a | 2.1% |
| 60652 | 6a | 2.1% |
| 60637 | 6a | 2.0% |
| 60646 | 6a | 1.9% |
| 60641 | 6a | 1.8% |
| 60655 | 6a | 1.8% |
| 60616 | 6b | 1.7% |
| 60625 | 6a | 1.7% |
| 60636 | 6a | 1.7% |
| 60647 | 6a | 1.7% |
| 60612 | 6a | 1.6% |
| 60621 | 6a | 1.6% |
| 60624 | 6a | 1.6% |
| 60631 | 6a | 1.6% |
| 60649 | 6b | 1.6% |
| 60644 | 6a | 1.5% |
| 60651 | 6a | 1.5% |
| 60614 | 6b | 1.4% |
| 60656 | 6a | 1.4% |
| 60106 | 6a | 1.2% |
| 60622 | 6a | 1.1% |
| 60607 | 6b | 1.0% |
| 60613 | 6b | 1.0% |
| 60615 | 6b | 1.0% |
| 60640 | 6a | 1.0% |
| 60645 | 6a | 1.0% |
| 60653 | 6b | 1.0% |
| 60657 | 6a | 1.0% |
| 60659 | 6a | 1.0% |
| 60626 | 6a | 0.8% |
| 60642 | 6a | 0.7% |
| 60605 | 6b | 0.6% |
| 60660 | 6a | 0.6% |
| 60610 | 6b | 0.5% |
| 60611 | 6b | 0.3% |
| 60601 | 6b | 0.2% |
| 60654 | 6b | 0.2% |
| 60661 | 6b | 0.1% |
| 60602 | 6b | 0.0% |
Vegetable planting calendar for Chicago
Dates are counted from the 30%-risk frost dates above (last frost Apr 17, first frost Nov 1). Shift a week later in cold spots or low-lying ground.
| Crop | Start indoors | Transplant / plant out | Direct sow | Fall crop sow/plant |
|---|---|---|---|---|
| Tomato | Feb 20 – Mar 6 | Apr 24 – May 8 | — | — |
| Pepper | Feb 6 – Feb 20 | May 1 – May 15 | — | — |
| Lettuce | Mar 6 – Mar 20 | Apr 3 – Apr 24 | Mar 20 – May 1 | Aug 23 – Sep 20 |
| Green Beans | — | — | Apr 24 – May 29 | Aug 9 – Aug 23 |
| Sweet Corn | — | — | Apr 24 – May 22 | — |
| Zucchini & Summer Squash | Mar 20 – Mar 27 | Apr 24 – May 8 | Apr 24 – May 15 | Aug 9 – Aug 23 |
| Cucumber | Mar 20 – Mar 27 | May 1 – May 8 | Apr 24 – May 15 | Aug 9 – Aug 23 |
| Carrot | — | — | Mar 27 – May 1 | Aug 9 – Aug 23 |
| Onion | Jan 23 – Feb 6 | Mar 20 – Apr 3 | — | — |
| Potato | — | Mar 20 – Apr 10 | — | — |
| Basil | Mar 6 – Mar 20 | May 1 – May 15 | May 1 – May 22 | — |
| Spinach | — | — | Mar 6 – Apr 3 | Sep 6 – Oct 4 |
| Kale | Feb 20 – Mar 6 | Mar 20 – Apr 10 | Mar 20 – Apr 10 | Aug 23 – Sep 20 |
| Broccoli | Feb 20 – Mar 6 | Apr 3 – Apr 24 | — | Aug 9 – Aug 23 |
| Peas | — | — | Mar 6 – Mar 27 | Aug 23 – Sep 6 |
| Eggplant | Feb 6 – Feb 20 | May 1 – May 15 | — | — |
| Cabbage | Feb 20 – Mar 6 | Mar 20 – Apr 3 | — | Aug 9 – Aug 23 |
| Radish | — | — | Mar 13 – May 1 | Sep 20 – Oct 18 |
| Strawberry | — | Mar 20 – Apr 10 | — | — |
| Beets | — | — | Mar 27 – May 8 | Aug 23 – Sep 6 |
Nearby cities in Illinois
- Cicero — zone 6a, last frost Apr 17, first frost Oct 26
- Evanston — zone 6a, last frost May 2, first frost Oct 14
- Schaumburg — zone 5b, last frost May 6, first frost Oct 8
- Naperville — zone 5b, last frost May 4, first frost Oct 11
- Joliet — zone 6a, last frost Apr 26, first frost Oct 20
- Waukegan — zone 6a, last frost May 4, first frost Oct 12
More: all Illinois cities · other zone 6a cities: Denver, CO, Milwaukee, WI, Colorado Springs, CO, Omaha, NE, Aurora, CO, Lincoln, NE, Fort Wayne, IN, Worcester, MA
Chicago gardening questions
When is the last frost in Chicago, IL?
Plan around Apr 17. At NOAA's Chicago Northerly Island, IL station, 4.1 mi from the city center, there is a 30% chance of a 32°F frost after that date. Half of springs have their last frost by Apr 10, and after Apr 25 the risk drops to about 1 in 10. A hard freeze (28°F) usually ends earlier, around Apr 1. The last frost is fairly predictable here: only 27 days separate the 90% and 10% dates (median for cities on this site: 36 days).
When should I plant tomatoes in Chicago, IL?
Start seeds indoors Feb 20 – Mar 6 and set transplants outside Apr 24 – May 8, once nights stay above 50°F and the soil is near 60°F. That leaves 198 days between the 30% frost dates, enough for most varieties including 80–85-day slicers. More: tomato planting dates by zone.
How long is the growing season in Chicago?
About 208 days without a 32°F frost in a typical (median) year. In 9 years out of 10 the season lasts at least 187 days, and in 1 year in 10 it runs 229 days or more. In fall there is a 10% chance of frost by Oct 24 and a 30% chance by Nov 1. That is the longest of the 14 Illinois cities on this site.
When should I plant a fall garden in Chicago?
Count back from the first fall frost (Nov 1): transplant broccoli Aug 9 – Aug 23; sow kale Aug 23 – Sep 20; sow lettuce Aug 23 – Sep 20; sow radishes Sep 20 – Oct 18. Hardy crops keep growing through light frosts; the median 28°F hard freeze here is Nov 15. How the math works: succession and fall planting.
Did Chicago's hardiness zone change on the 2023 map?
No. Going by the zone that covers most of the city's land, Chicago is zone 6a on both the 2012 and the 2023 USDA maps (PRISM/OSU ZIP listings). About 42% of U.S. ZIP codes kept their half-zone in 2023. Why the 2023 map is warmer.
Is all of Chicago in zone 6a?
No. Zone 6a covers about 89% of the city's land; the rest is in 6b (11%), measured across the city's 55 ZIP codes. Check your own ZIP code in the table above or with the ZIP lookup.