Waukegan, Illinois: planting zone & frost dates
Waukegan 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 May 4 and the first fall frost around Oct 12.
Frost dates
| Probability | Last spring frost (32°F) | First fall frost (32°F) |
|---|---|---|
| Safer (10% risk) | May 14 | Sep 30 |
| Typical planning date (30% risk) | May 4 | Oct 12 |
| Median (50%) | Apr 30 | Oct 19 |
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 WAUKEGAN, IL (USC00119029), 1.6 mi (2.5 km) from the city center and 16 ft lower than the city center (-5 m). Record used for the 1991–2020 normals: 12 years.
Why your yard may differ from the station: microclimates.
Hardiness zone across Waukegan
Waukegan spans more than one half-zone. Share of the city's land area by zone (via its 5 ZIP codes): 6a (96%), 5b (4%). The headline zone is the one covering the most land. Look up your ZIP for your exact zone.
Vegetable planting calendar for Waukegan
Dates are counted from the 30%-risk frost dates above (last frost May 4, first frost Oct 12). Shift a week later in cold spots or low-lying ground.
| Crop | Start indoors | Transplant / plant out | Direct sow | Fall crop sow/plant |
|---|---|---|---|---|
| Tomato | Mar 9 – Mar 23 | May 11 – May 25 | — | — |
| Pepper | Feb 23 – Mar 9 | May 18 – Jun 1 | — | — |
| Lettuce | Mar 23 – Apr 6 | Apr 20 – May 11 | Apr 6 – May 18 | Aug 3 – Aug 31 |
| Green Beans | — | — | May 11 – Jun 15 | Jul 20 – Aug 3 |
| Sweet Corn | — | — | May 11 – Jun 8 | — |
| Zucchini & Summer Squash | Apr 6 – Apr 13 | May 11 – May 25 | May 11 – Jun 1 | Jul 20 – Aug 3 |
| Cucumber | Apr 6 – Apr 13 | May 18 – May 25 | May 11 – Jun 1 | Jul 20 – Aug 3 |
| Carrot | — | — | Apr 13 – May 18 | Jul 20 – Aug 3 |
| Onion | Feb 9 – Feb 23 | Apr 6 – Apr 20 | — | — |
| Potato | — | Apr 6 – Apr 27 | — | — |
| Basil | Mar 23 – Apr 6 | May 18 – Jun 1 | May 18 – Jun 8 | — |
| Spinach | — | — | Mar 23 – Apr 20 | Aug 17 – Sep 14 |
| Kale | Mar 9 – Mar 23 | Apr 6 – Apr 27 | Apr 6 – Apr 27 | Aug 3 – Aug 31 |
| Broccoli | Mar 9 – Mar 23 | Apr 20 – May 11 | — | Jul 20 – Aug 3 |
| Peas | — | — | Mar 23 – Apr 13 | Aug 3 – Aug 17 |
| Eggplant | Feb 23 – Mar 9 | May 18 – Jun 1 | — | — |
| Cabbage | Mar 9 – Mar 23 | Apr 6 – Apr 20 | — | Jul 20 – Aug 3 |
| Radish | — | — | Mar 30 – May 18 | Aug 31 – Sep 28 |
| Strawberry | — | Apr 6 – Apr 27 | — | — |
| Beets | — | — | Apr 13 – May 25 | Aug 3 – Aug 17 |
Nearby cities in Illinois
- Evanston — zone 6a, last frost May 2, first frost Oct 14
- Schaumburg — zone 5b, last frost May 6, first frost Oct 8
- Cicero — zone 6a, last frost Apr 17, first frost Oct 26
- Elgin — zone 5b, last frost May 1, first frost Oct 12
- Chicago — zone 6a, last frost Apr 17, first frost Nov 1
- Naperville — zone 5b, last frost May 4, first frost Oct 11
More: all Illinois cities · other zone 6a cities: Chicago, IL, Denver, CO, Milwaukee, WI, Colorado Springs, CO, Omaha, NE, Aurora, CO, Lincoln, NE, Fort Wayne, IN
Waukegan gardening questions
When is the last frost in Waukegan, IL?
Plan around May 4. At NOAA's Waukegan, IL station, 1.6 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 30, and after May 14 the risk drops to about 1 in 10. A hard freeze (28°F) usually ends earlier, around Apr 20. The 90% and 10% dates are 29 days apart, close to the 36-day median for cities on this site.
When should I plant tomatoes in Waukegan, IL?
Start seeds indoors Mar 9 – Mar 23 and set transplants outside May 11 – May 25, once nights stay above 50°F and the soil is near 60°F. That leaves 161 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 Waukegan?
About 170 days without a 32°F frost in a typical (median) year. In 9 years out of 10 the season lasts at least 150 days, and in 1 year in 10 it runs 190 days or more. In fall there is a 10% chance of frost by Sep 30 and a 30% chance by Oct 12. That ranks 12th longest of 14 Illinois cities on this site.
When should I plant a fall garden in Waukegan?
Count back from the first fall frost (Oct 12): transplant broccoli Jul 20 – Aug 3; sow kale Aug 3 – Aug 31; sow lettuce Aug 3 – Aug 31; sow radishes Aug 31 – Sep 28. Hardy crops keep growing through light frosts; the median 28°F hard freeze here is Oct 30. How the math works: succession and fall planting.
Did Waukegan's hardiness zone change on the 2023 map?
Yes. Most of Waukegan was zone 5b on the 2012 map and is zone 6a on the 2023 map — half a zone warmer, like about 56% of U.S. ZIP codes. The shift comes from a newer 1991–2020 averaging period plus more weather stations and better mapping; it does not mean last frost comes earlier. Why the 2023 map is warmer.
Is all of Waukegan in zone 6a?
No. Zone 6a covers about 96% of the city's land; the rest is in 5b (4%), measured across the city's 5 ZIP codes. Check your own ZIP code in the table above or with the ZIP lookup.