Mercer, WI frost dates
Last spring frostMay 25median date
First fall frostSep 21median date
Growing season119 daysfrost-free
Hardiness zone4aZone 4a
How Mercer compares
- In 8 years out of 10, the last spring frost in Mercer falls between May 8 and June 9, a 32-day window. The first fall frost falls between September 3 and October 6.
- The median last frost is 20 days later than the Wisconsin median of May 5.
- Its 119-day growing season is among the shortest of the 749 Wisconsin places with a regular frost season.
- The last frost is 13 days later than the zone 4a median of May 12. Hardiness zones measure winter cold, not season length, so use these dates rather than a zone 4a chart.
- The weather station records an average of 195 nights a year at or below 32°F.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | May 8 |
| 50% (median) | May 25 |
| 10% (safe for tender plants) | June 9 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | September 3 |
| 50% (median) | September 21 |
| 90% (late) | October 6 |
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 Mercer, WI
Mercer, WI frost dates — last frost May 25, first frost Sep 21, zone 4a. whenisthelastfrost.com
Crop
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Start indoors: Mar 2 to Mar 16Transplant outside: Apr 27 to May 11
Start indoors: Mar 16 to Mar 30Transplant outside: Jun 8 to Jun 22
Start indoors: Mar 16 to Mar 30Transplant outside: Jun 8 to Jun 22
Start indoors: Mar 30 to Apr 13Transplant outside: Jun 1 to Jun 15
Start indoors: Mar 30 to Apr 13Transplant outside: May 4 to May 18Sow outdoors: Apr 27 to Jun 1Plant for fall: Jul 27 to Aug 24
Start indoors: Mar 30 to Apr 13Transplant outside: Apr 27 to May 11Sow outdoors: Apr 27 to May 11Plant for fall: Jul 13 to Aug 3
Start indoors: Mar 30 to Apr 13Transplant outside: May 11 to May 25Plant for fall: Jun 15 to Jul 6
Start indoors: Mar 30 to Apr 13Transplant outside: May 4 to May 18Plant for fall: Jun 15 to Jul 6
Start indoors: Mar 30 to Apr 13Transplant outside: May 11 to May 25Plant for fall: Jun 15 to Jul 6
Start indoors: Apr 13 to Apr 27Transplant outside: Jun 15 to Jun 29Sow outdoors: Jun 15 to Jun 29
Start indoors: Apr 13 to Apr 27Transplant outside: Jun 1 to Jun 15
Sow outdoors: Apr 13 to May 4Plant for fall: Jun 29 to Jul 20
Sow outdoors: Apr 13 to May 4Plant for fall: Jul 27 to Aug 17
Sow outdoors: Apr 20 to Jun 1Plant for fall: Aug 10 to Aug 31
Start indoors: Apr 27 to May 4Transplant outside: Jun 8 to Jun 15Sow outdoors: Jun 1 to Jun 15Plant for fall: Jul 6 to Jul 20
Start indoors: Apr 27 to May 4Sow outdoors: Jun 1 to Jun 15Plant for fall: Jul 13 to Jul 27
Start indoors: Apr 27 to May 4Sow outdoors: Jun 1 to Jun 15
Start indoors: Apr 27 to May 4Transplant outside: Jun 8 to Jun 22
Sow outdoors: May 4 to Jun 1Plant for fall: Jun 29 to Jul 13
Sow outdoors: May 4 to Jun 1Plant for fall: Jul 13 to Jul 27
Sow outdoors: May 4 to May 25
Sow outdoors: May 11 to Jun 8Plant for fall: Jul 13 to Jul 27
Sow outdoors: May 11 to Jun 1Plant for fall: Jul 27 to Aug 17
Sow outdoors: Jun 1 to Jun 22
Sow outdoors: Jun 1 to Jun 15
Transplant outside: Jun 8 to Jun 29
Plant for fall: Sep 7 to Oct 12
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Mercer, WI
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Mar 2 – Mar 16 | Apr 27 – May 11 | — | — |
| Peppers | Mar 16 – Mar 30 | Jun 8 – Jun 22 | — | — |
| Eggplant | Mar 16 – Mar 30 | Jun 8 – Jun 22 | — | — |
| Tomatoes | Mar 30 – Apr 13 | Jun 1 – Jun 15 | — | — |
| Lettuce | Mar 30 – Apr 13 | May 4 – May 18 | Apr 27 – Jun 1 | Jul 27 – Aug 24 |
| Kale | Mar 30 – Apr 13 | Apr 27 – May 11 | Apr 27 – May 11 | Jul 13 – Aug 3 |
| Broccoli | Mar 30 – Apr 13 | May 11 – May 25 | — | Jun 15 – Jul 6 |
| Cabbage | Mar 30 – Apr 13 | May 4 – May 18 | — | Jun 15 – Jul 6 |
| Cauliflower | Mar 30 – Apr 13 | May 11 – May 25 | — | Jun 15 – Jul 6 |
| Okra | Apr 13 – Apr 27 | Jun 15 – Jun 29 | Jun 15 – Jun 29 | — |
| Basil | Apr 13 – Apr 27 | Jun 1 – Jun 15 | — | — |
| Peas | — | — | Apr 13 – May 4 | Jun 29 – Jul 20 |
| Spinach | — | — | Apr 13 – May 4 | Jul 27 – Aug 17 |
| Radishes | — | — | Apr 20 – Jun 1 | Aug 10 – Aug 31 |
| Cucumbers | Apr 27 – May 4 | Jun 8 – Jun 15 | Jun 1 – Jun 15 | Jul 6 – Jul 20 |
| Zucchini & Summer Squash | Apr 27 – May 4 | — | Jun 1 – Jun 15 | Jul 13 – Jul 27 |
| Winter Squash & Pumpkins | Apr 27 – May 4 | — | Jun 1 – Jun 15 | — |
| Melons & Watermelon | Apr 27 – May 4 | Jun 8 – Jun 22 | — | — |
| Carrots | — | — | May 4 – Jun 1 | Jun 29 – Jul 13 |
| Beets | — | — | May 4 – Jun 1 | Jul 13 – Jul 27 |
| Potatoes | — | — | May 4 – May 25 | — |
| Swiss Chard | — | — | May 11 – Jun 8 | Jul 13 – Jul 27 |
| Cilantro | — | — | May 11 – Jun 1 | Jul 27 – Aug 17 |
| Green Beans | — | — | Jun 1 – Jun 22 | — |
| Sweet Corn | — | — | Jun 1 – Jun 15 | — |
| Sweet Potatoes | — | Jun 8 – Jun 29 | — | — |
| Garlic | — | — | — | Sep 7 – Oct 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 Rest Lake, WI weather station, 16 km away (elevation 1,611 ft (491 m)).
Frost dates near Mercer
- Manitowish Waters May 25 · Sep 21
- Presque Isle May 25 · Sep 21
- Lac Du Flambeau May 23 · Sep 27
- Gile May 24 · Sep 28
- Montreal May 24 · Sep 28
- Iron Belt May 24 · Sep 28
- Hurley May 24 · Sep 28
- Boulder Junction May 25 · Sep 21
- Upson May 23 · Oct 1
- Butternut May 22 · Sep 24
Frequently asked questions
When is the last frost in Mercer, WI?
The median last spring frost in Mercer, WI is May 25. There is still about a 10% chance of frost after June 9, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Mercer, WI?
The median first fall frost is September 21, with about a 10% chance of frost before September 3.
How long is the growing season in Mercer, WI?
About 119 days between the median last spring frost and first fall frost.
What planting zone is Mercer, WI?
Mercer, WI is in USDA hardiness zone 4a.