Rock Falls, IL frost dates
Last spring frostApr 21median date
First fall frostOct 19median date
Growing season181 daysfrost-free
Hardiness zone5bZone 5b
How Rock Falls compares
- In 8 years out of 10, the last spring frost in Rock Falls falls between April 7 and May 5, a 28-day window. The first fall frost falls between October 4 and October 30.
- The median last frost is 4 days later than the Illinois median of Apr 17.
- Its 181-day growing season is longer than 35% of the 1,287 Illinois places with a regular frost season (state median 187 days).
- The last frost is 10 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 138 nights a year at or below 32°F.
- Compared with Rockford, IL, 76 km away, the last frost here is 3 days earlier than there and the growing season is 5 days longer.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | April 7 |
| 50% (median) | April 21 |
| 10% (safe for tender plants) | May 5 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | October 4 |
| 50% (median) | October 19 |
| 90% (late) | October 30 |
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 Rock Falls, IL
Rock Falls, IL frost dates — last frost Apr 21, first frost Oct 19, zone 5b. whenisthelastfrost.com
Crop
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Start indoors: Jan 27 to Feb 10Transplant outside: Mar 24 to Apr 7
Start indoors: Feb 10 to Feb 24Transplant outside: May 5 to May 19
Start indoors: Feb 10 to Feb 24Transplant outside: May 5 to May 19
Start indoors: Feb 24 to Mar 10Transplant outside: Apr 28 to May 12
Start indoors: Feb 24 to Mar 10Transplant outside: Mar 31 to Apr 14Sow outdoors: Mar 24 to Apr 28Plant for fall: Aug 24 to Sep 21
Start indoors: Feb 24 to Mar 10Transplant outside: Mar 24 to Apr 7Sow outdoors: Mar 24 to Apr 7Plant for fall: Aug 10 to Aug 31
Start indoors: Feb 24 to Mar 10Transplant outside: Apr 7 to Apr 21Plant for fall: Jul 13 to Aug 3
Start indoors: Feb 24 to Mar 10Transplant outside: Mar 31 to Apr 14Plant for fall: Jul 13 to Aug 3
Start indoors: Feb 24 to Mar 10Transplant outside: Apr 7 to Apr 21Plant for fall: Jul 13 to Aug 3
Start indoors: Mar 10 to Mar 24Transplant outside: May 12 to May 26Sow outdoors: May 12 to May 26
Start indoors: Mar 10 to Mar 24Transplant outside: Apr 28 to May 12
Sow outdoors: Mar 10 to Mar 31Plant for fall: Jul 27 to Aug 17
Sow outdoors: Mar 10 to Mar 31Plant for fall: Aug 24 to Sep 14
Sow outdoors: Mar 17 to Apr 28Plant for fall: Sep 7 to Sep 28
Start indoors: Mar 24 to Mar 31Transplant outside: May 5 to May 12Sow outdoors: Apr 28 to May 12Plant for fall: Aug 3 to Aug 17
Start indoors: Mar 24 to Mar 31Sow outdoors: Apr 28 to May 12Plant for fall: Aug 10 to Aug 24
Start indoors: Mar 24 to Mar 31Sow outdoors: Apr 28 to May 12
Start indoors: Mar 24 to Mar 31Transplant outside: May 5 to May 19
Sow outdoors: Mar 31 to Apr 28Plant for fall: Jul 27 to Aug 10
Sow outdoors: Mar 31 to Apr 28Plant for fall: Aug 10 to Aug 24
Sow outdoors: Mar 31 to Apr 21
Sow outdoors: Apr 7 to May 5Plant for fall: Aug 10 to Aug 24
Sow outdoors: Apr 7 to Apr 28Plant for fall: Aug 24 to Sep 14
Sow outdoors: Apr 28 to May 19Plant for fall: Aug 3 to Aug 17
Sow outdoors: Apr 28 to May 12
Transplant outside: May 5 to May 26
Plant for fall: Oct 5 to Nov 9
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Rock Falls, IL
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Jan 27 – Feb 10 | Mar 24 – Apr 7 | — | — |
| Peppers | Feb 10 – Feb 24 | May 5 – May 19 | — | — |
| Eggplant | Feb 10 – Feb 24 | May 5 – May 19 | — | — |
| Tomatoes | Feb 24 – Mar 10 | Apr 28 – May 12 | — | — |
| Lettuce | Feb 24 – Mar 10 | Mar 31 – Apr 14 | Mar 24 – Apr 28 | Aug 24 – Sep 21 |
| Kale | Feb 24 – Mar 10 | Mar 24 – Apr 7 | Mar 24 – Apr 7 | Aug 10 – Aug 31 |
| Broccoli | Feb 24 – Mar 10 | Apr 7 – Apr 21 | — | Jul 13 – Aug 3 |
| Cabbage | Feb 24 – Mar 10 | Mar 31 – Apr 14 | — | Jul 13 – Aug 3 |
| Cauliflower | Feb 24 – Mar 10 | Apr 7 – Apr 21 | — | Jul 13 – Aug 3 |
| Okra | Mar 10 – Mar 24 | May 12 – May 26 | May 12 – May 26 | — |
| Basil | Mar 10 – Mar 24 | Apr 28 – May 12 | — | — |
| Peas | — | — | Mar 10 – Mar 31 | Jul 27 – Aug 17 |
| Spinach | — | — | Mar 10 – Mar 31 | Aug 24 – Sep 14 |
| Radishes | — | — | Mar 17 – Apr 28 | Sep 7 – Sep 28 |
| Cucumbers | Mar 24 – Mar 31 | May 5 – May 12 | Apr 28 – May 12 | Aug 3 – Aug 17 |
| Zucchini & Summer Squash | Mar 24 – Mar 31 | — | Apr 28 – May 12 | Aug 10 – Aug 24 |
| Winter Squash & Pumpkins | Mar 24 – Mar 31 | — | Apr 28 – May 12 | — |
| Melons & Watermelon | Mar 24 – Mar 31 | May 5 – May 19 | — | — |
| Carrots | — | — | Mar 31 – Apr 28 | Jul 27 – Aug 10 |
| Beets | — | — | Mar 31 – Apr 28 | Aug 10 – Aug 24 |
| Potatoes | — | — | Mar 31 – Apr 21 | — |
| Swiss Chard | — | — | Apr 7 – May 5 | Aug 10 – Aug 24 |
| Cilantro | — | — | Apr 7 – Apr 28 | Aug 24 – Sep 14 |
| Green Beans | — | — | Apr 28 – May 19 | Aug 3 – Aug 17 |
| Sweet Corn | — | — | Apr 28 – May 12 | — |
| Sweet Potatoes | — | May 5 – May 26 | — | — |
| Garlic | — | — | — | Oct 5 – Nov 9 |
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 Dixon 1w, IL weather station, 17 km away (elevation 659 ft (201 m)).
Frost dates near Rock Falls
- Sterling Apr 21 · Oct 19
- Galt Apr 26 · Oct 13
- Harmon Apr 24 · Oct 14
- Deer Grove Apr 24 · Oct 14
- Tampico Apr 24 · Oct 14
- Dixon Apr 21 · Oct 19
- Lyndon Apr 26 · Oct 13
- Woosung Apr 21 · Oct 19
- Eldena Apr 21 · Oct 19
- Milledgeville Apr 29 · Oct 7
Frequently asked questions
When is the last frost in Rock Falls, IL?
The median last spring frost in Rock Falls, IL is April 21. There is still about a 10% chance of frost after May 5, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Rock Falls, IL?
The median first fall frost is October 19, with about a 10% chance of frost before October 4.
How long is the growing season in Rock Falls, IL?
About 181 days between the median last spring frost and first fall frost.
What planting zone is Rock Falls, IL?
Rock Falls, IL is in USDA hardiness zone 5b.