Rio, IL frost dates
Last spring frostApr 20median date
First fall frostOct 19median date
Growing season182 daysfrost-free
Hardiness zone5bZone 5b
How Rio compares
- In 8 years out of 10, the last spring frost in Rio falls between April 6 and May 5, a 29-day window. The first fall frost falls between October 4 and October 30.
- The median last frost is 3 days later than the Illinois median of Apr 17.
- Its 182-day growing season is longer than 37% of the 1,287 Illinois places with a regular frost season (state median 187 days).
- The last frost is 11 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 129 nights a year at or below 32°F.
- Compared with Davenport, IA, 53 km away, the last frost here is 3 days earlier than there and the growing season is 7 days longer.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | April 6 |
| 50% (median) | April 20 |
| 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 Rio, IL
Rio, IL frost dates — last frost Apr 20, first frost Oct 19, zone 5b. whenisthelastfrost.com
Crop
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Start indoors: Jan 26 to Feb 9Transplant outside: Mar 23 to Apr 6
Start indoors: Feb 9 to Feb 23Transplant outside: May 4 to May 18
Start indoors: Feb 9 to Feb 23Transplant outside: May 4 to May 18
Start indoors: Feb 23 to Mar 9Transplant outside: Apr 27 to May 11
Start indoors: Feb 23 to Mar 9Transplant outside: Mar 30 to Apr 13Sow outdoors: Mar 23 to Apr 27Plant for fall: Aug 24 to Sep 21
Start indoors: Feb 23 to Mar 9Transplant outside: Mar 23 to Apr 6Sow outdoors: Mar 23 to Apr 6Plant for fall: Aug 10 to Aug 31
Start indoors: Feb 23 to Mar 9Transplant outside: Apr 6 to Apr 20Plant for fall: Jul 13 to Aug 3
Start indoors: Feb 23 to Mar 9Transplant outside: Mar 30 to Apr 13Plant for fall: Jul 13 to Aug 3
Start indoors: Feb 23 to Mar 9Transplant outside: Apr 6 to Apr 20Plant for fall: Jul 13 to Aug 3
Start indoors: Mar 9 to Mar 23Transplant outside: May 11 to May 25Sow outdoors: May 11 to May 25
Start indoors: Mar 9 to Mar 23Transplant outside: Apr 27 to May 11
Sow outdoors: Mar 9 to Mar 30Plant for fall: Jul 27 to Aug 17
Sow outdoors: Mar 9 to Mar 30Plant for fall: Aug 24 to Sep 14
Sow outdoors: Mar 16 to Apr 27Plant for fall: Sep 7 to Sep 28
Start indoors: Mar 23 to Mar 30Transplant outside: May 4 to May 11Sow outdoors: Apr 27 to May 11Plant for fall: Aug 3 to Aug 17
Start indoors: Mar 23 to Mar 30Sow outdoors: Apr 27 to May 11Plant for fall: Aug 10 to Aug 24
Start indoors: Mar 23 to Mar 30Sow outdoors: Apr 27 to May 11
Start indoors: Mar 23 to Mar 30Transplant outside: May 4 to May 18
Sow outdoors: Mar 30 to Apr 27Plant for fall: Jul 27 to Aug 10
Sow outdoors: Mar 30 to Apr 27Plant for fall: Aug 10 to Aug 24
Sow outdoors: Mar 30 to Apr 20
Sow outdoors: Apr 6 to May 4Plant for fall: Aug 10 to Aug 24
Sow outdoors: Apr 6 to Apr 27Plant for fall: Aug 24 to Sep 14
Sow outdoors: Apr 27 to May 18Plant for fall: Aug 3 to Aug 17
Sow outdoors: Apr 27 to May 11
Transplant outside: May 4 to May 25
Plant for fall: Oct 5 to Nov 9
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Rio, IL
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Jan 26 – Feb 9 | Mar 23 – Apr 6 | — | — |
| Peppers | Feb 9 – Feb 23 | May 4 – May 18 | — | — |
| Eggplant | Feb 9 – Feb 23 | May 4 – May 18 | — | — |
| Tomatoes | Feb 23 – Mar 9 | Apr 27 – May 11 | — | — |
| Lettuce | Feb 23 – Mar 9 | Mar 30 – Apr 13 | Mar 23 – Apr 27 | Aug 24 – Sep 21 |
| Kale | Feb 23 – Mar 9 | Mar 23 – Apr 6 | Mar 23 – Apr 6 | Aug 10 – Aug 31 |
| Broccoli | Feb 23 – Mar 9 | Apr 6 – Apr 20 | — | Jul 13 – Aug 3 |
| Cabbage | Feb 23 – Mar 9 | Mar 30 – Apr 13 | — | Jul 13 – Aug 3 |
| Cauliflower | Feb 23 – Mar 9 | Apr 6 – Apr 20 | — | Jul 13 – Aug 3 |
| Okra | Mar 9 – Mar 23 | May 11 – May 25 | May 11 – May 25 | — |
| Basil | Mar 9 – Mar 23 | Apr 27 – May 11 | — | — |
| Peas | — | — | Mar 9 – Mar 30 | Jul 27 – Aug 17 |
| Spinach | — | — | Mar 9 – Mar 30 | Aug 24 – Sep 14 |
| Radishes | — | — | Mar 16 – Apr 27 | Sep 7 – Sep 28 |
| Cucumbers | Mar 23 – Mar 30 | May 4 – May 11 | Apr 27 – May 11 | Aug 3 – Aug 17 |
| Zucchini & Summer Squash | Mar 23 – Mar 30 | — | Apr 27 – May 11 | Aug 10 – Aug 24 |
| Winter Squash & Pumpkins | Mar 23 – Mar 30 | — | Apr 27 – May 11 | — |
| Melons & Watermelon | Mar 23 – Mar 30 | May 4 – May 18 | — | — |
| Carrots | — | — | Mar 30 – Apr 27 | Jul 27 – Aug 10 |
| Beets | — | — | Mar 30 – Apr 27 | Aug 10 – Aug 24 |
| Potatoes | — | — | Mar 30 – Apr 20 | — |
| Swiss Chard | — | — | Apr 6 – May 4 | Aug 10 – Aug 24 |
| Cilantro | — | — | Apr 6 – Apr 27 | Aug 24 – Sep 14 |
| Green Beans | — | — | Apr 27 – May 18 | Aug 3 – Aug 17 |
| Sweet Corn | — | — | Apr 27 – May 11 | — |
| Sweet Potatoes | — | May 4 – May 25 | — | — |
| 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 Galesburg, IL weather station, 18 km away (elevation 761 ft (232 m)).
Frost dates near Rio
- North Henderson Apr 20 · Oct 19
- Alpha Apr 28 · Oct 12
- Henderson Apr 20 · Oct 19
- New Windsor Apr 22 · Oct 19
- Woodhull Apr 28 · Oct 12
- Oneida Apr 28 · Oct 12
- Wataga Apr 20 · Oct 19
- Alexis Apr 22 · Oct 15
- Ophiem Apr 28 · Oct 12
- Galesburg Apr 20 · Oct 19
Frequently asked questions
When is the last frost in Rio, IL?
The median last spring frost in Rio, IL is April 20. 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 Rio, 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 Rio, IL?
About 182 days between the median last spring frost and first fall frost.
What planting zone is Rio, IL?
Rio, IL is in USDA hardiness zone 5b.