Algonquin, IL frost dates
Last spring frostApr 26median date
First fall frostOct 18median date
Growing season175 daysfrost-free
Hardiness zone5bZone 5b
How Algonquin compares
- In 8 years out of 10, the last spring frost in Algonquin falls between April 12 and May 12, a 30-day window. The first fall frost falls between October 3 and October 31.
- The median last frost is 9 days later than the Illinois median of Apr 17.
- Its 175-day growing season is longer than 16% of the 1,287 Illinois places with a regular frost season (state median 187 days).
- The last frost is 5 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 139 nights a year at or below 32°F.
- Algonquin shares its weather station with Elgin, IL, 14 km away, so the two have the same frost dates.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | April 12 |
| 50% (median) | April 26 |
| 10% (safe for tender plants) | May 12 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | October 3 |
| 50% (median) | October 18 |
| 90% (late) | October 31 |
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 Algonquin, IL
Algonquin, IL frost dates — last frost Apr 26, first frost Oct 18, zone 5b. whenisthelastfrost.com
Crop
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Start indoors: Feb 1 to Feb 15Transplant outside: Mar 29 to Apr 12
Start indoors: Feb 15 to Mar 1Transplant outside: May 10 to May 24
Start indoors: Feb 15 to Mar 1Transplant outside: May 10 to May 24
Start indoors: Mar 1 to Mar 15Transplant outside: May 3 to May 17
Start indoors: Mar 1 to Mar 15Transplant outside: Apr 5 to Apr 19Sow outdoors: Mar 29 to May 3Plant for fall: Aug 23 to Sep 20
Start indoors: Mar 1 to Mar 15Transplant outside: Mar 29 to Apr 12Sow outdoors: Mar 29 to Apr 12Plant for fall: Aug 9 to Aug 30
Start indoors: Mar 1 to Mar 15Transplant outside: Apr 12 to Apr 26Plant for fall: Jul 12 to Aug 2
Start indoors: Mar 1 to Mar 15Transplant outside: Apr 5 to Apr 19Plant for fall: Jul 12 to Aug 2
Start indoors: Mar 1 to Mar 15Transplant outside: Apr 12 to Apr 26Plant for fall: Jul 12 to Aug 2
Start indoors: Mar 15 to Mar 29Transplant outside: May 17 to May 31Sow outdoors: May 17 to May 31
Start indoors: Mar 15 to Mar 29Transplant outside: May 3 to May 17
Sow outdoors: Mar 15 to Apr 5Plant for fall: Jul 26 to Aug 16
Sow outdoors: Mar 15 to Apr 5Plant for fall: Aug 23 to Sep 13
Sow outdoors: Mar 22 to May 3Plant for fall: Sep 6 to Sep 27
Start indoors: Mar 29 to Apr 5Transplant outside: May 10 to May 17Sow outdoors: May 3 to May 17Plant for fall: Aug 2 to Aug 16
Start indoors: Mar 29 to Apr 5Sow outdoors: May 3 to May 17Plant for fall: Aug 9 to Aug 23
Start indoors: Mar 29 to Apr 5Sow outdoors: May 3 to May 17
Start indoors: Mar 29 to Apr 5Transplant outside: May 10 to May 24
Sow outdoors: Apr 5 to May 3Plant for fall: Jul 26 to Aug 9
Sow outdoors: Apr 5 to May 3Plant for fall: Aug 9 to Aug 23
Sow outdoors: Apr 5 to Apr 26
Sow outdoors: Apr 12 to May 10Plant for fall: Aug 9 to Aug 23
Sow outdoors: Apr 12 to May 3Plant for fall: Aug 23 to Sep 13
Sow outdoors: May 3 to May 24Plant for fall: Aug 2 to Aug 16
Sow outdoors: May 3 to May 17
Transplant outside: May 10 to May 31
Plant for fall: Oct 4 to Nov 8
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Algonquin, IL
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Feb 1 – Feb 15 | Mar 29 – Apr 12 | — | — |
| Peppers | Feb 15 – Mar 1 | May 10 – May 24 | — | — |
| Eggplant | Feb 15 – Mar 1 | May 10 – May 24 | — | — |
| Tomatoes | Mar 1 – Mar 15 | May 3 – May 17 | — | — |
| Lettuce | Mar 1 – Mar 15 | Apr 5 – Apr 19 | Mar 29 – May 3 | Aug 23 – Sep 20 |
| Kale | Mar 1 – Mar 15 | Mar 29 – Apr 12 | Mar 29 – Apr 12 | Aug 9 – Aug 30 |
| Broccoli | Mar 1 – Mar 15 | Apr 12 – Apr 26 | — | Jul 12 – Aug 2 |
| Cabbage | Mar 1 – Mar 15 | Apr 5 – Apr 19 | — | Jul 12 – Aug 2 |
| Cauliflower | Mar 1 – Mar 15 | Apr 12 – Apr 26 | — | Jul 12 – Aug 2 |
| Okra | Mar 15 – Mar 29 | May 17 – May 31 | May 17 – May 31 | — |
| Basil | Mar 15 – Mar 29 | May 3 – May 17 | — | — |
| Peas | — | — | Mar 15 – Apr 5 | Jul 26 – Aug 16 |
| Spinach | — | — | Mar 15 – Apr 5 | Aug 23 – Sep 13 |
| Radishes | — | — | Mar 22 – May 3 | Sep 6 – Sep 27 |
| Cucumbers | Mar 29 – Apr 5 | May 10 – May 17 | May 3 – May 17 | Aug 2 – Aug 16 |
| Zucchini & Summer Squash | Mar 29 – Apr 5 | — | May 3 – May 17 | Aug 9 – Aug 23 |
| Winter Squash & Pumpkins | Mar 29 – Apr 5 | — | May 3 – May 17 | — |
| Melons & Watermelon | Mar 29 – Apr 5 | May 10 – May 24 | — | — |
| Carrots | — | — | Apr 5 – May 3 | Jul 26 – Aug 9 |
| Beets | — | — | Apr 5 – May 3 | Aug 9 – Aug 23 |
| Potatoes | — | — | Apr 5 – Apr 26 | — |
| Swiss Chard | — | — | Apr 12 – May 10 | Aug 9 – Aug 23 |
| Cilantro | — | — | Apr 12 – May 3 | Aug 23 – Sep 13 |
| Green Beans | — | — | May 3 – May 24 | Aug 2 – Aug 16 |
| Sweet Corn | — | — | May 3 – May 17 | — |
| Sweet Potatoes | — | May 10 – May 31 | — | — |
| Garlic | — | — | — | Oct 4 – Nov 8 |
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 Elgin, IL weather station, 11 km away (elevation 764 ft (233 m)).
Frost dates near Algonquin
- Lake In The Hills Apr 25 · Oct 22
- Carpentersville Apr 26 · Oct 18
- Dundee Apr 26 · Oct 18
- Fox River Grove Apr 25 · Oct 19
- Cary May 1 · Oct 11
- Gilberts Apr 26 · Oct 18
- Huntley Apr 25 · Oct 22
- Crystal Lake Apr 25 · Oct 22
- Elgin Apr 26 · Oct 18
- Barrington Apr 25 · Oct 19
Frequently asked questions
When is the last frost in Algonquin, IL?
The median last spring frost in Algonquin, IL is April 26. There is still about a 10% chance of frost after May 12, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Algonquin, IL?
The median first fall frost is October 18, with about a 10% chance of frost before October 3.
How long is the growing season in Algonquin, IL?
About 175 days between the median last spring frost and first fall frost.
What planting zone is Algonquin, IL?
Algonquin, IL is in USDA hardiness zone 5b.