Willmar, MN planting zone & frost dates
Willmar is in USDA hardiness zone 4b. The last spring frost usually comes around April 30 and the first fall frost around October 7, for a growing season of about 159 days.
Planting calendar for Willmar
Dates are counted from the average last spring frost (April 30) using the typical timing recommended by U.S. extension services. Warm-season crops go out only after the danger of frost has passed and the soil has warmed.
| Crop | When |
|---|---|
| Tomatoes | Start seeds indoors: Mar 5 – Mar 19 Transplant outdoors: May 7 – May 14 |
| Peppers | Start seeds indoors: Feb 19 – Mar 5 Transplant outdoors: May 14 – May 21 |
| Eggplant | Start seeds indoors: Feb 19 – Mar 5 Transplant outdoors: May 14 – May 21 |
| Broccoli | Start seeds indoors: Feb 19 – Mar 5 Transplant outdoors: Apr 2 – Apr 16 |
| Cabbage | Start seeds indoors: Feb 19 – Mar 5 Transplant outdoors: Apr 2 – Apr 16 |
| Onions (sets) | Plant outdoors: Apr 2 – Apr 16 |
| Peas | Sow outdoors: Mar 19 – Apr 2 |
| Spinach | Sow outdoors: Mar 19 – Apr 2 |
| Lettuce | Sow outdoors: Apr 2 – Apr 16 |
| Carrots | Sow outdoors: Apr 2 – Apr 16 |
| Potatoes | Plant outdoors: Apr 2 – Apr 16 |
| Beans | Sow outdoors: May 7 – May 14 |
| Sweet corn | Sow outdoors: May 7 – May 14 |
| Cucumbers | Sow outdoors: May 7 – May 14 |
| Squash & zucchini | Sow outdoors: May 7 – May 14 |
| Basil | Start seeds indoors: Mar 19 – Apr 2 Transplant outdoors: May 7 – May 14 |
Fall garden: cool-season crops like lettuce, spinach and kale can be sown again around Aug 12 (8 weeks before the average first fall frost on Oct 7).
Useful for zone 4b gardens
- Seed starting kit with dome — to start seeds indoors before the last frost
- LED grow light for seedlings — stops leggy seedlings
- Frost cloth / plant covers — for late spring and early fall frosts
- Soil thermometer — warm-season crops need soil above 60°F
- Cold frame / mini greenhouse — adds weeks to a short season
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Frost risk in detail
| 90% chance | 50% chance | 10% chance | |
|---|---|---|---|
| Last 32°F frost in spring is after | Apr 16 | Apr 30 | May 13 |
| First 32°F frost in fall is before | Oct 21 | Oct 7 | Sep 23 |
How to read it: in spring there is a 10% chance of a frost after May 13, so that is a safe date for tender plants. In fall there is a 10% chance of frost before September 23. A hard freeze (28°F) usually ends around April 19.
Hardiness zone by ZIP code in Willmar
- 56201 zone 4b
Nearby cities
- Hutchinson zone 4b, last frost Apr 28
- Alexandria zone 4b, last frost May 2
- Sartell zone 4b, last frost May 7
- Saint Cloud zone 4b, last frost May 7
- Sauk Rapids zone 4b, last frost May 7
- New Ulm zone 5a, last frost Apr 29
- Marshall zone 5a, last frost May 5
- Buffalo zone 4b, last frost Apr 30
Questions
What growing zone is Willmar, MN?
Willmar is in USDA Plant Hardiness Zone 4b (average extreme winter low -25°F to -20°F), according to the USDA 2023 map.
When is the last frost in Willmar?
The average last spring frost (32°F) in Willmar is April 30. There is still a 10% chance of frost until May 13.
When can I plant tomatoes in Willmar?
Transplant tomatoes outdoors 1–2 weeks after the average last frost: around May 7 – May 14. Start seeds indoors 6–8 weeks before the last frost.
Frost dates: NOAA U.S. Climate Normals 1991–2020, station Willmar Wwtp, MN (USC00219004), 1.7 km (1.1 mi) from the city center, elevation 335 m, based on 19 years of records. Hardiness zone: USDA Plant Hardiness Zone Map 2023 for the ZIP code nearest to the city center. Microclimates (valleys, hills, cities, coasts) can be warmer or colder: check the local forecast before planting. How we calculate the data.