Aurora, Illinois: planting zone & frost dates
Aurora is in USDA plant hardiness zone 5b, where the average coldest winter night reaches -15 to -10°F (-26.1 to -23.3°C). The typical last spring frost is around Apr 25 and the first fall frost around Oct 18.
Frost dates
| Probability | Last spring frost (32°F) | First fall frost (32°F) |
|---|---|---|
| Safer (10% risk) | May 4 | Oct 9 |
| Typical planning date (30% risk) | Apr 25 | Oct 18 |
| Median (50%) | Apr 19 | Oct 23 |
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 AURORA, IL (USC00110338), 1.6 mi (2.5 km) from the city center and 59 ft lower than the city center (-18 m). Record used for the 1991–2020 normals: 28 years.
Why your yard may differ from the station: microclimates.
Hardiness zone across Aurora
All 7 ZIP codes covering Aurora are in zone 5b.
Vegetable planting calendar for Aurora
Dates are counted from the 30%-risk frost dates above (last frost Apr 25, first frost Oct 18). 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 28 – Mar 14 | May 2 – May 16 | — | — |
| Pepper | Feb 14 – Feb 28 | May 9 – May 23 | — | — |
| Lettuce | Mar 14 – Mar 28 | Apr 11 – May 2 | Mar 28 – May 9 | Aug 9 – Sep 6 |
| Green Beans | — | — | May 2 – Jun 6 | Jul 26 – Aug 9 |
| Sweet Corn | — | — | May 2 – May 30 | — |
| Zucchini & Summer Squash | Mar 28 – Apr 4 | May 2 – May 16 | May 2 – May 23 | Jul 26 – Aug 9 |
| Cucumber | Mar 28 – Apr 4 | May 9 – May 16 | May 2 – May 23 | Jul 26 – Aug 9 |
| Carrot | — | — | Apr 4 – May 9 | Jul 26 – Aug 9 |
| Onion | Jan 31 – Feb 14 | Mar 28 – Apr 11 | — | — |
| Potato | — | Mar 28 – Apr 18 | — | — |
| Basil | Mar 14 – Mar 28 | May 9 – May 23 | May 9 – May 30 | — |
| Spinach | — | — | Mar 14 – Apr 11 | Aug 23 – Sep 20 |
| Kale | Feb 28 – Mar 14 | Mar 28 – Apr 18 | Mar 28 – Apr 18 | Aug 9 – Sep 6 |
| Broccoli | Feb 28 – Mar 14 | Apr 11 – May 2 | — | Jul 26 – Aug 9 |
| Peas | — | — | Mar 14 – Apr 4 | Aug 9 – Aug 23 |
| Eggplant | Feb 14 – Feb 28 | May 9 – May 23 | — | — |
| Cabbage | Feb 28 – Mar 14 | Mar 28 – Apr 11 | — | Jul 26 – Aug 9 |
| Radish | — | — | Mar 21 – May 9 | Sep 6 – Oct 4 |
| Strawberry | — | Mar 28 – Apr 18 | — | — |
| Beets | — | — | Apr 4 – May 16 | Aug 9 – Aug 23 |
Nearby cities in Illinois
- Naperville — zone 5b, last frost May 4, first frost Oct 11
- Elgin — zone 5b, last frost May 1, first frost Oct 12
- Joliet — zone 6a, last frost Apr 26, first frost Oct 20
- Schaumburg — zone 5b, last frost May 6, first frost Oct 8
- Cicero — zone 6a, last frost Apr 17, first frost Oct 26
- Chicago — zone 6a, last frost Apr 17, first frost Nov 1
More: all Illinois cities · other zone 5b cities: Madison, WI, Des Moines, IA, Fort Collins, CO, Naperville, IL, Rockford, IL, Elgin, IL, Greeley, CO, Green Bay, WI
Aurora gardening questions
When is the last frost in Aurora, IL?
Plan around Apr 25. At NOAA's Aurora, 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 19, and after May 4 the risk drops to about 1 in 10. A hard freeze (28°F) usually ends earlier, around Apr 8. 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 Aurora, IL?
Start seeds indoors Feb 28 – Mar 14 and set transplants outside May 2 – May 16, once nights stay above 50°F and the soil is near 60°F. That leaves 176 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 Aurora?
About 185 days without a 32°F frost in a typical (median) year. In 9 years out of 10 the season lasts at least 164 days, and in 1 year in 10 it runs 205 days or more. In fall there is a 10% chance of frost by Oct 9 and a 30% chance by Oct 18. That ranks 7th longest of 14 Illinois cities on this site.
When should I plant a fall garden in Aurora?
Count back from the first fall frost (Oct 18): transplant broccoli Jul 26 – Aug 9; sow kale Aug 9 – Sep 6; sow lettuce Aug 9 – Sep 6; sow radishes Sep 6 – Oct 4. Hardy crops keep growing through light frosts; the median 28°F hard freeze here is Nov 2. How the math works: succession and fall planting.
Did Aurora's hardiness zone change on the 2023 map?
No. Going by the zone that covers most of the city's land, Aurora is zone 5b 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.
How does Aurora compare with Naperville, IL?
Both are in zone 5b. The typical last spring frost in Aurora (Apr 25) comes about 9 days earlier than in Naperville, IL (May 4), 7 miles away, and the first fall frost is Oct 18 versus Oct 11. The two cities use different NOAA stations.