Illinois City, IL frost dates
Last spring frostApr 18median date
First fall frostOct 24median date
Growing season189 daysfrost-free
Hardiness zone5bZone 5b
How Illinois City compares
- In 8 years out of 10, the last spring frost in Illinois City falls between April 5 and May 2, a 27-day window. The first fall frost falls between October 11 and November 6.
- The median last frost is 1 day later than the Illinois median of Apr 17.
- Its 189-day growing season is longer than 54% of the 1,287 Illinois places with a regular frost season (state median 187 days).
- The last frost is 13 days earlier than the zone 5b median of May 1. Hardiness zones measure winter cold, not season length, so use these dates rather than a zone 5b chart.
- The weather station records an average of 131 nights a year at or below 32°F.
- Compared with Davenport, IA, 32 km away, the last frost here is 5 days earlier than there and the growing season is 14 days longer.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | April 5 |
| 50% (median) | April 18 |
| 10% (safe for tender plants) | May 2 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | October 11 |
| 50% (median) | October 24 |
| 90% (late) | November 6 |
Frost here means 32°F (0°C). A median date means half of years have their last frost earlier and half later.
Planting calendar for Illinois City, IL
Illinois City, IL frost dates — last frost Apr 18, first frost Oct 24, zone 5b. whenisthelastfrost.com
Crop
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Start indoors: Jan 24 to Feb 7Transplant outside: Mar 21 to Apr 4
Start indoors: Feb 7 to Feb 21Transplant outside: May 2 to May 16
Start indoors: Feb 7 to Feb 21Transplant outside: May 2 to May 16
Start indoors: Feb 21 to Mar 7Transplant outside: Apr 25 to May 9
Start indoors: Feb 21 to Mar 7Transplant outside: Mar 28 to Apr 11Sow outdoors: Mar 21 to Apr 25Plant for fall: Aug 29 to Sep 26
Start indoors: Feb 21 to Mar 7Transplant outside: Mar 21 to Apr 4Sow outdoors: Mar 21 to Apr 4Plant for fall: Aug 15 to Sep 5
Start indoors: Feb 21 to Mar 7Transplant outside: Apr 4 to Apr 18Plant for fall: Jul 18 to Aug 8
Start indoors: Feb 21 to Mar 7Transplant outside: Mar 28 to Apr 11Plant for fall: Jul 18 to Aug 8
Start indoors: Feb 21 to Mar 7Transplant outside: Apr 4 to Apr 18Plant for fall: Jul 18 to Aug 8
Start indoors: Mar 7 to Mar 21Transplant outside: May 9 to May 23Sow outdoors: May 9 to May 23
Start indoors: Mar 7 to Mar 21Transplant outside: Apr 25 to May 9
Sow outdoors: Mar 7 to Mar 28Plant for fall: Aug 1 to Aug 22
Sow outdoors: Mar 7 to Mar 28Plant for fall: Aug 29 to Sep 19
Sow outdoors: Mar 14 to Apr 25Plant for fall: Sep 12 to Oct 3
Start indoors: Mar 21 to Mar 28Transplant outside: May 2 to May 9Sow outdoors: Apr 25 to May 9Plant for fall: Aug 8 to Aug 22
Start indoors: Mar 21 to Mar 28Sow outdoors: Apr 25 to May 9Plant for fall: Aug 15 to Aug 29
Start indoors: Mar 21 to Mar 28Sow outdoors: Apr 25 to May 9
Start indoors: Mar 21 to Mar 28Transplant outside: May 2 to May 16
Sow outdoors: Mar 28 to Apr 25Plant for fall: Aug 1 to Aug 15
Sow outdoors: Mar 28 to Apr 25Plant for fall: Aug 15 to Aug 29
Sow outdoors: Mar 28 to Apr 18
Sow outdoors: Apr 4 to May 2Plant for fall: Aug 15 to Aug 29
Sow outdoors: Apr 4 to Apr 25Plant for fall: Aug 29 to Sep 19
Sow outdoors: Apr 25 to May 16Plant for fall: Aug 8 to Aug 22
Sow outdoors: Apr 25 to May 9
Transplant outside: May 2 to May 23
Plant for fall: Oct 10 to Nov 14
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Illinois City, IL
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Jan 24 – Feb 7 | Mar 21 – Apr 4 | — | — |
| Peppers | Feb 7 – Feb 21 | May 2 – May 16 | — | — |
| Eggplant | Feb 7 – Feb 21 | May 2 – May 16 | — | — |
| Tomatoes | Feb 21 – Mar 7 | Apr 25 – May 9 | — | — |
| Lettuce | Feb 21 – Mar 7 | Mar 28 – Apr 11 | Mar 21 – Apr 25 | Aug 29 – Sep 26 |
| Kale | Feb 21 – Mar 7 | Mar 21 – Apr 4 | Mar 21 – Apr 4 | Aug 15 – Sep 5 |
| Broccoli | Feb 21 – Mar 7 | Apr 4 – Apr 18 | — | Jul 18 – Aug 8 |
| Cabbage | Feb 21 – Mar 7 | Mar 28 – Apr 11 | — | Jul 18 – Aug 8 |
| Cauliflower | Feb 21 – Mar 7 | Apr 4 – Apr 18 | — | Jul 18 – Aug 8 |
| Okra | Mar 7 – Mar 21 | May 9 – May 23 | May 9 – May 23 | — |
| Basil | Mar 7 – Mar 21 | Apr 25 – May 9 | — | — |
| Peas | — | — | Mar 7 – Mar 28 | Aug 1 – Aug 22 |
| Spinach | — | — | Mar 7 – Mar 28 | Aug 29 – Sep 19 |
| Radishes | — | — | Mar 14 – Apr 25 | Sep 12 – Oct 3 |
| Cucumbers | Mar 21 – Mar 28 | May 2 – May 9 | Apr 25 – May 9 | Aug 8 – Aug 22 |
| Zucchini & Summer Squash | Mar 21 – Mar 28 | — | Apr 25 – May 9 | Aug 15 – Aug 29 |
| Winter Squash & Pumpkins | Mar 21 – Mar 28 | — | Apr 25 – May 9 | — |
| Melons & Watermelon | Mar 21 – Mar 28 | May 2 – May 16 | — | — |
| Carrots | — | — | Mar 28 – Apr 25 | Aug 1 – Aug 15 |
| Beets | — | — | Mar 28 – Apr 25 | Aug 15 – Aug 29 |
| Potatoes | — | — | Mar 28 – Apr 18 | — |
| Swiss Chard | — | — | Apr 4 – May 2 | Aug 15 – Aug 29 |
| Cilantro | — | — | Apr 4 – Apr 25 | Aug 29 – Sep 19 |
| Green Beans | — | — | Apr 25 – May 16 | Aug 8 – Aug 22 |
| Sweet Corn | — | — | Apr 25 – May 9 | — |
| Sweet Potatoes | — | May 2 – May 23 | — | — |
| Garlic | — | — | — | Oct 10 – Nov 14 |
Dates come from the median frost dates and common extension-service timing. Adjust for your soil temperature, microclimate and the varieties you grow.
About these dates
Based on 1991–2020 NOAA climate normals for the Illinois City Dam, IL weather station, 11 km away (elevation 551 ft (168 m)).
Frost dates near Illinois City
- Buffalo Prairie Apr 18 · Oct 24
- Taylor Ridge Apr 24 · Oct 18
- Andalusia Apr 19 · Oct 22
- Joy Apr 22 · Oct 19
- New Boston Apr 14 · Oct 24
- Reynolds Apr 22 · Oct 19
- Aledo Apr 22 · Oct 19
- Milan Apr 24 · Oct 18
- Preemption Apr 22 · Oct 19
- Matherville Apr 22 · Oct 19
Frequently asked questions
When is the last frost in Illinois City, IL?
The median last spring frost in Illinois City, IL is April 18. There is still about a 10% chance of frost after May 2, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Illinois City, IL?
The median first fall frost is October 24, with about a 10% chance of frost before October 11.
How long is the growing season in Illinois City, IL?
About 189 days between the median last spring frost and first fall frost.
What planting zone is Illinois City, IL?
Illinois City, IL is in USDA hardiness zone 5b.