Irma, WI frost dates
Last spring frostMay 11median date
First fall frostSep 30median date
Growing season142 daysfrost-free
Hardiness zone4bZone 4b
How Irma compares
- In 8 years out of 10, the last spring frost in Irma falls between April 29 and May 27, a 28-day window. The first fall frost falls between September 17 and October 12.
- The median last frost is 6 days later than the Wisconsin median of May 5.
- Its 142-day growing season is longer than 18% of the 749 Wisconsin places with a regular frost season (state median 155 days).
- The last frost is typical for zone 4b, where the median is May 8.
- The weather station records an average of 182 nights a year at or below 32°F.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | April 29 |
| 50% (median) | May 11 |
| 10% (safe for tender plants) | May 27 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | September 17 |
| 50% (median) | September 30 |
| 90% (late) | October 12 |
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 Irma, WI
Irma, WI frost dates — last frost May 11, first frost Sep 30, zone 4b. whenisthelastfrost.com
Crop
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Start indoors: Feb 16 to Mar 2Transplant outside: Apr 13 to Apr 27
Start indoors: Mar 2 to Mar 16Transplant outside: May 25 to Jun 8
Start indoors: Mar 2 to Mar 16Transplant outside: May 25 to Jun 8
Start indoors: Mar 16 to Mar 30Transplant outside: May 18 to Jun 1
Start indoors: Mar 16 to Mar 30Transplant outside: Apr 20 to May 4Sow outdoors: Apr 13 to May 18Plant for fall: Aug 5 to Sep 2
Start indoors: Mar 16 to Mar 30Transplant outside: Apr 13 to Apr 27Sow outdoors: Apr 13 to Apr 27Plant for fall: Jul 22 to Aug 12
Start indoors: Mar 16 to Mar 30Transplant outside: Apr 27 to May 11Plant for fall: Jun 24 to Jul 15
Start indoors: Mar 16 to Mar 30Transplant outside: Apr 20 to May 4Plant for fall: Jun 24 to Jul 15
Start indoors: Mar 16 to Mar 30Transplant outside: Apr 27 to May 11Plant for fall: Jun 24 to Jul 15
Start indoors: Mar 30 to Apr 13Transplant outside: Jun 1 to Jun 15Sow outdoors: Jun 1 to Jun 15
Start indoors: Mar 30 to Apr 13Transplant outside: May 18 to Jun 1
Sow outdoors: Mar 30 to Apr 20Plant for fall: Jul 8 to Jul 29
Sow outdoors: Mar 30 to Apr 20Plant for fall: Aug 5 to Aug 26
Sow outdoors: Apr 6 to May 18Plant for fall: Aug 19 to Sep 9
Start indoors: Apr 13 to Apr 20Transplant outside: May 25 to Jun 1Sow outdoors: May 18 to Jun 1Plant for fall: Jul 15 to Jul 29
Start indoors: Apr 13 to Apr 20Sow outdoors: May 18 to Jun 1Plant for fall: Jul 22 to Aug 5
Start indoors: Apr 13 to Apr 20Sow outdoors: May 18 to Jun 1
Start indoors: Apr 13 to Apr 20Transplant outside: May 25 to Jun 8
Sow outdoors: Apr 20 to May 18Plant for fall: Jul 8 to Jul 22
Sow outdoors: Apr 20 to May 18Plant for fall: Jul 22 to Aug 5
Sow outdoors: Apr 20 to May 11
Sow outdoors: Apr 27 to May 25Plant for fall: Jul 22 to Aug 5
Sow outdoors: Apr 27 to May 18Plant for fall: Aug 5 to Aug 26
Sow outdoors: May 18 to Jun 8Plant for fall: Jul 15 to Jul 29
Sow outdoors: May 18 to Jun 1
Transplant outside: May 25 to Jun 15
Plant for fall: Sep 16 to Oct 21
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Irma, WI
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Feb 16 – Mar 2 | Apr 13 – Apr 27 | — | — |
| Peppers | Mar 2 – Mar 16 | May 25 – Jun 8 | — | — |
| Eggplant | Mar 2 – Mar 16 | May 25 – Jun 8 | — | — |
| Tomatoes | Mar 16 – Mar 30 | May 18 – Jun 1 | — | — |
| Lettuce | Mar 16 – Mar 30 | Apr 20 – May 4 | Apr 13 – May 18 | Aug 5 – Sep 2 |
| Kale | Mar 16 – Mar 30 | Apr 13 – Apr 27 | Apr 13 – Apr 27 | Jul 22 – Aug 12 |
| Broccoli | Mar 16 – Mar 30 | Apr 27 – May 11 | — | Jun 24 – Jul 15 |
| Cabbage | Mar 16 – Mar 30 | Apr 20 – May 4 | — | Jun 24 – Jul 15 |
| Cauliflower | Mar 16 – Mar 30 | Apr 27 – May 11 | — | Jun 24 – Jul 15 |
| Okra | Mar 30 – Apr 13 | Jun 1 – Jun 15 | Jun 1 – Jun 15 | — |
| Basil | Mar 30 – Apr 13 | May 18 – Jun 1 | — | — |
| Peas | — | — | Mar 30 – Apr 20 | Jul 8 – Jul 29 |
| Spinach | — | — | Mar 30 – Apr 20 | Aug 5 – Aug 26 |
| Radishes | — | — | Apr 6 – May 18 | Aug 19 – Sep 9 |
| Cucumbers | Apr 13 – Apr 20 | May 25 – Jun 1 | May 18 – Jun 1 | Jul 15 – Jul 29 |
| Zucchini & Summer Squash | Apr 13 – Apr 20 | — | May 18 – Jun 1 | Jul 22 – Aug 5 |
| Winter Squash & Pumpkins | Apr 13 – Apr 20 | — | May 18 – Jun 1 | — |
| Melons & Watermelon | Apr 13 – Apr 20 | May 25 – Jun 8 | — | — |
| Carrots | — | — | Apr 20 – May 18 | Jul 8 – Jul 22 |
| Beets | — | — | Apr 20 – May 18 | Jul 22 – Aug 5 |
| Potatoes | — | — | Apr 20 – May 11 | — |
| Swiss Chard | — | — | Apr 27 – May 25 | Jul 22 – Aug 5 |
| Cilantro | — | — | Apr 27 – May 18 | Aug 5 – Aug 26 |
| Green Beans | — | — | May 18 – Jun 8 | Jul 15 – Jul 29 |
| Sweet Corn | — | — | May 18 – Jun 1 | — |
| Sweet Potatoes | — | May 25 – Jun 15 | — | — |
| Garlic | — | — | — | Sep 16 – Oct 21 |
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 Merrill, WI weather station, 19 km away (elevation 1,250 ft (381 m)).
Frost dates near Irma
- Gleason May 11 · Sep 30
- Tomahawk May 10 · Oct 4
- Merrill May 11 · Sep 30
- Heafford Junction May 10 · Oct 4
- Summit Lake Jun 3 · Sep 18
- Brokaw May 6 · Oct 4
- Tripoli May 13 · Oct 3
- Harshaw May 26 · Sep 23
- Deerbrook May 14 · Sep 30
- Rib Lake May 11 · Oct 1
Frequently asked questions
When is the last frost in Irma, WI?
The median last spring frost in Irma, WI is May 11. There is still about a 10% chance of frost after May 27, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Irma, WI?
The median first fall frost is September 30, with about a 10% chance of frost before September 17.
How long is the growing season in Irma, WI?
About 142 days between the median last spring frost and first fall frost.
What planting zone is Irma, WI?
Irma, WI is in USDA hardiness zone 4b.