Sullivan, IL frost dates
Last spring frostApr 15median date
First fall frostOct 22median date
Growing season190 daysfrost-free
Hardiness zone6aZone 6a
How Sullivan compares
- In 8 years out of 10, the last spring frost in Sullivan falls between April 2 and April 30, a 28-day window. The first fall frost falls between October 6 and November 2.
- The median last frost is 2 days earlier than the Illinois median of Apr 17.
- Its 190-day growing season is longer than 57% of the 1,287 Illinois places with a regular frost season (state median 187 days).
- The last frost is 14 days earlier than the zone 6a median of Apr 29. Hardiness zones measure winter cold, not season length, so use these dates rather than a zone 6a chart.
- The weather station records an average of 122 nights a year at or below 32°F.
- Compared with Decatur, IL, 42 km away, the last frost here is 1 day later than there and the growing season is 3 days shorter.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | April 2 |
| 50% (median) | April 15 |
| 10% (safe for tender plants) | April 30 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | October 6 |
| 50% (median) | October 22 |
| 90% (late) | November 2 |
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 Sullivan, IL
Sullivan, IL frost dates — last frost Apr 15, first frost Oct 22, zone 6a. whenisthelastfrost.com
Crop
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Start indoors: Jan 21 to Feb 4Transplant outside: Mar 18 to Apr 1
Start indoors: Feb 4 to Feb 18Transplant outside: Apr 29 to May 13
Start indoors: Feb 4 to Feb 18Transplant outside: Apr 29 to May 13
Start indoors: Feb 18 to Mar 4Transplant outside: Apr 22 to May 6
Start indoors: Feb 18 to Mar 4Transplant outside: Mar 25 to Apr 8Sow outdoors: Mar 18 to Apr 22Plant for fall: Aug 27 to Sep 24
Start indoors: Feb 18 to Mar 4Transplant outside: Mar 18 to Apr 1Sow outdoors: Mar 18 to Apr 1Plant for fall: Aug 13 to Sep 3
Start indoors: Feb 18 to Mar 4Transplant outside: Apr 1 to Apr 15Plant for fall: Jul 16 to Aug 6
Start indoors: Feb 18 to Mar 4Transplant outside: Mar 25 to Apr 8Plant for fall: Jul 16 to Aug 6
Start indoors: Feb 18 to Mar 4Transplant outside: Apr 1 to Apr 15Plant for fall: Jul 16 to Aug 6
Start indoors: Mar 4 to Mar 18Transplant outside: May 6 to May 20Sow outdoors: May 6 to May 20
Start indoors: Mar 4 to Mar 18Transplant outside: Apr 22 to May 6
Sow outdoors: Mar 4 to Mar 25Plant for fall: Jul 30 to Aug 20
Sow outdoors: Mar 4 to Mar 25Plant for fall: Aug 27 to Sep 17
Sow outdoors: Mar 11 to Apr 22Plant for fall: Sep 10 to Oct 1
Start indoors: Mar 18 to Mar 25Transplant outside: Apr 29 to May 6Sow outdoors: Apr 22 to May 6Plant for fall: Aug 6 to Aug 20
Start indoors: Mar 18 to Mar 25Sow outdoors: Apr 22 to May 6Plant for fall: Aug 13 to Aug 27
Start indoors: Mar 18 to Mar 25Sow outdoors: Apr 22 to May 6
Start indoors: Mar 18 to Mar 25Transplant outside: Apr 29 to May 13
Sow outdoors: Mar 25 to Apr 22Plant for fall: Jul 30 to Aug 13
Sow outdoors: Mar 25 to Apr 22Plant for fall: Aug 13 to Aug 27
Sow outdoors: Mar 25 to Apr 15
Sow outdoors: Apr 1 to Apr 29Plant for fall: Aug 13 to Aug 27
Sow outdoors: Apr 1 to Apr 22Plant for fall: Aug 27 to Sep 17
Sow outdoors: Apr 22 to May 13Plant for fall: Aug 6 to Aug 20
Sow outdoors: Apr 22 to May 6
Transplant outside: Apr 29 to May 20
Plant for fall: Oct 8 to Nov 12
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Sullivan, IL
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Jan 21 – Feb 4 | Mar 18 – Apr 1 | — | — |
| Peppers | Feb 4 – Feb 18 | Apr 29 – May 13 | — | — |
| Eggplant | Feb 4 – Feb 18 | Apr 29 – May 13 | — | — |
| Tomatoes | Feb 18 – Mar 4 | Apr 22 – May 6 | — | — |
| Lettuce | Feb 18 – Mar 4 | Mar 25 – Apr 8 | Mar 18 – Apr 22 | Aug 27 – Sep 24 |
| Kale | Feb 18 – Mar 4 | Mar 18 – Apr 1 | Mar 18 – Apr 1 | Aug 13 – Sep 3 |
| Broccoli | Feb 18 – Mar 4 | Apr 1 – Apr 15 | — | Jul 16 – Aug 6 |
| Cabbage | Feb 18 – Mar 4 | Mar 25 – Apr 8 | — | Jul 16 – Aug 6 |
| Cauliflower | Feb 18 – Mar 4 | Apr 1 – Apr 15 | — | Jul 16 – Aug 6 |
| Okra | Mar 4 – Mar 18 | May 6 – May 20 | May 6 – May 20 | — |
| Basil | Mar 4 – Mar 18 | Apr 22 – May 6 | — | — |
| Peas | — | — | Mar 4 – Mar 25 | Jul 30 – Aug 20 |
| Spinach | — | — | Mar 4 – Mar 25 | Aug 27 – Sep 17 |
| Radishes | — | — | Mar 11 – Apr 22 | Sep 10 – Oct 1 |
| Cucumbers | Mar 18 – Mar 25 | Apr 29 – May 6 | Apr 22 – May 6 | Aug 6 – Aug 20 |
| Zucchini & Summer Squash | Mar 18 – Mar 25 | — | Apr 22 – May 6 | Aug 13 – Aug 27 |
| Winter Squash & Pumpkins | Mar 18 – Mar 25 | — | Apr 22 – May 6 | — |
| Melons & Watermelon | Mar 18 – Mar 25 | Apr 29 – May 13 | — | — |
| Carrots | — | — | Mar 25 – Apr 22 | Jul 30 – Aug 13 |
| Beets | — | — | Mar 25 – Apr 22 | Aug 13 – Aug 27 |
| Potatoes | — | — | Mar 25 – Apr 15 | — |
| Swiss Chard | — | — | Apr 1 – Apr 29 | Aug 13 – Aug 27 |
| Cilantro | — | — | Apr 1 – Apr 22 | Aug 27 – Sep 17 |
| Green Beans | — | — | Apr 22 – May 13 | Aug 6 – Aug 20 |
| Sweet Corn | — | — | Apr 22 – May 6 | — |
| Sweet Potatoes | — | Apr 29 – May 20 | — | — |
| Garlic | — | — | — | Oct 8 – Nov 12 |
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 Sullivan 3s, IL weather station, 4 km away (elevation 640 ft (195 m)).
Frost dates near Sullivan
- Bethany Apr 15 · Oct 22
- Gays Apr 16 · Oct 22
- Lovington Apr 15 · Oct 22
- Findlay Apr 10 · Oct 24
- Arthur Apr 15 · Oct 20
- Windsor Apr 16 · Oct 22
- Dalton City Apr 16 · Oct 22
- Hammond Apr 15 · Oct 20
- Shelbyville Apr 10 · Oct 24
- Mattoon Apr 11 · Oct 29
Frequently asked questions
When is the last frost in Sullivan, IL?
The median last spring frost in Sullivan, IL is April 15. There is still about a 10% chance of frost after April 30, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Sullivan, IL?
The median first fall frost is October 22, with about a 10% chance of frost before October 6.
How long is the growing season in Sullivan, IL?
About 190 days between the median last spring frost and first fall frost.
What planting zone is Sullivan, IL?
Sullivan, IL is in USDA hardiness zone 6a.