Fort Atkinson, WI planting zone & frost dates
Fort Atkinson is in USDA hardiness zone 5b. The last spring frost usually comes around April 28 and the first fall frost around October 13, for a growing season of about 166 days.
Planting calendar for Fort Atkinson
Dates are counted from the average last spring frost (April 28) 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 3 – Mar 17 Transplant outdoors: May 5 – May 12 |
| Peppers | Start seeds indoors: Feb 17 – Mar 3 Transplant outdoors: May 12 – May 19 |
| Eggplant | Start seeds indoors: Feb 17 – Mar 3 Transplant outdoors: May 12 – May 19 |
| Broccoli | Start seeds indoors: Feb 17 – Mar 3 Transplant outdoors: Mar 31 – Apr 14 |
| Cabbage | Start seeds indoors: Feb 17 – Mar 3 Transplant outdoors: Mar 31 – Apr 14 |
| Onions (sets) | Plant outdoors: Mar 31 – Apr 14 |
| Peas | Sow outdoors: Mar 17 – Mar 31 |
| Spinach | Sow outdoors: Mar 17 – Mar 31 |
| Lettuce | Sow outdoors: Mar 31 – Apr 14 |
| Carrots | Sow outdoors: Mar 31 – Apr 14 |
| Potatoes | Plant outdoors: Mar 31 – Apr 14 |
| Beans | Sow outdoors: May 5 – May 12 |
| Sweet corn | Sow outdoors: May 5 – May 12 |
| Cucumbers | Sow outdoors: May 5 – May 12 |
| Squash & zucchini | Sow outdoors: May 5 – May 12 |
| Basil | Start seeds indoors: Mar 17 – Mar 31 Transplant outdoors: May 5 – May 12 |
Fall garden: cool-season crops like lettuce, spinach and kale can be sown again around Aug 18 (8 weeks before the average first fall frost on Oct 13).
Useful for zone 5b 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 14 | Apr 28 | May 17 |
| First 32°F frost in fall is before | Oct 26 | Oct 13 | Sep 29 |
How to read it: in spring there is a 10% chance of a frost after May 17, so that is a safe date for tender plants. In fall there is a 10% chance of frost before September 29. A hard freeze (28°F) usually ends around April 16.
Hardiness zone by ZIP code in Fort Atkinson
- 53538 zone 5b
Nearby cities
- Whitewater zone 5b, last frost May 2
- Watertown zone 5b, last frost Apr 28
- Janesville zone 5b, last frost Apr 26
- Stoughton zone 5b, last frost Apr 30
- Oconomowoc zone 5b, last frost Apr 30
- Sun Prairie zone 5a, last frost May 1
- Beloit zone 5b, last frost May 1
- Beaver Dam zone 5a, last frost May 2
Questions
What growing zone is Fort Atkinson, WI?
Fort Atkinson is in USDA Plant Hardiness Zone 5b (average extreme winter low -15°F to -10°F), according to the USDA 2023 map.
When is the last frost in Fort Atkinson?
The average last spring frost (32°F) in Fort Atkinson is April 28. There is still a 10% chance of frost until May 17.
When can I plant tomatoes in Fort Atkinson?
Transplant tomatoes outdoors 1–2 weeks after the average last frost: around May 5 – May 12. Start seeds indoors 6–8 weeks before the last frost.
Frost dates: NOAA U.S. Climate Normals 1991–2020, station Ft Atkinson, WI (USC00472869), 3.2 km (2.0 mi) from the city center, elevation 244 m, based on 30 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.