Rockford, Illinois: planting zone & frost dates
Rockford 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 30 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 8 | Oct 2 |
| Typical planning date (30% risk) | Apr 30 | Oct 12 |
| Median (50%) | Apr 24 | Oct 17 |
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 ROCKFORD GTR ROCKFORD AP, IL (USW00094822), 4.8 mi (7.8 km) from the city center and 3 ft higher than the city center (+1 m). Record used for the 1991–2020 normals: 30 years.
Why your yard may differ from the station: microclimates.
Hardiness zone across Rockford
All 9 ZIP codes covering Rockford are in zone 5b.
Vegetable planting calendar for Rockford
Dates are counted from the 30%-risk frost dates above (last frost Apr 30, 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 5 – Mar 19 | May 7 – May 21 | — | — |
| Pepper | Feb 19 – Mar 5 | May 14 – May 28 | — | — |
| Lettuce | Mar 19 – Apr 2 | Apr 16 – May 7 | Apr 2 – May 14 | Aug 3 – Aug 31 |
| Green Beans | — | — | May 7 – Jun 11 | Jul 20 – Aug 3 |
| Sweet Corn | — | — | May 7 – Jun 4 | — |
| Zucchini & Summer Squash | Apr 2 – Apr 9 | May 7 – May 21 | May 7 – May 28 | Jul 20 – Aug 3 |
| Cucumber | Apr 2 – Apr 9 | May 14 – May 21 | May 7 – May 28 | Jul 20 – Aug 3 |
| Carrot | — | — | Apr 9 – May 14 | Jul 20 – Aug 3 |
| Onion | Feb 5 – Feb 19 | Apr 2 – Apr 16 | — | — |
| Potato | — | Apr 2 – Apr 23 | — | — |
| Basil | Mar 19 – Apr 2 | May 14 – May 28 | May 14 – Jun 4 | — |
| Spinach | — | — | Mar 19 – Apr 16 | Aug 17 – Sep 14 |
| Kale | Mar 5 – Mar 19 | Apr 2 – Apr 23 | Apr 2 – Apr 23 | Aug 3 – Aug 31 |
| Broccoli | Mar 5 – Mar 19 | Apr 16 – May 7 | — | Jul 20 – Aug 3 |
| Peas | — | — | Mar 19 – Apr 9 | Aug 3 – Aug 17 |
| Eggplant | Feb 19 – Mar 5 | May 14 – May 28 | — | — |
| Cabbage | Mar 5 – Mar 19 | Apr 2 – Apr 16 | — | Jul 20 – Aug 3 |
| Radish | — | — | Mar 26 – May 14 | Aug 31 – Sep 28 |
| Strawberry | — | Apr 2 – Apr 23 | — | — |
| Beets | — | — | Apr 9 – May 21 | Aug 3 – Aug 17 |
Nearby cities in Illinois
- Elgin — zone 5b, last frost May 1, first frost Oct 12
- Aurora — zone 5b, last frost Apr 25, first frost Oct 18
- 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 5b cities: Madison, WI, Des Moines, IA, Aurora, IL, Fort Collins, CO, Naperville, IL, Elgin, IL, Greeley, CO, Green Bay, WI
Rockford gardening questions
When is the last frost in Rockford, IL?
Plan around Apr 30. At NOAA's Rockford Gtr Rockford Airport, IL station, 4.8 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 24, and after May 8 the risk drops to about 1 in 10. A hard freeze (28°F) usually ends earlier, around Apr 13. The last frost is fairly predictable here: only 28 days separate the 90% and 10% dates (median for cities on this site: 36 days).
When should I plant tomatoes in Rockford, IL?
Start seeds indoors Mar 5 – Mar 19 and set transplants outside May 7 – May 21, once nights stay above 50°F and the soil is near 60°F. That leaves 165 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 Rockford?
About 174 days without a 32°F frost in a typical (median) year. In 9 years out of 10 the season lasts at least 154 days, and in 1 year in 10 it runs 192 days or more. In fall there is a 10% chance of frost by Oct 2 and a 30% chance by Oct 12. That ranks 9th longest of 14 Illinois cities on this site.
When should I plant a fall garden in Rockford?
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 28. How the math works: succession and fall planting.
Did Rockford's hardiness zone change on the 2023 map?
No. Going by the zone that covers most of the city's land, Rockford 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 Rockford compare with Elgin, IL?
Both are in zone 5b. The typical last spring frost in Rockford (Apr 30) comes about the same time as in Elgin, IL (May 1), 41 miles away, and the first fall frost is Oct 12 versus Oct 12. The two cities use different NOAA stations.