Grafton, WI planting zone & frost dates
Grafton is in USDA hardiness zone 6a. The last spring frost usually comes around April 23 and the first fall frost around October 24, for a growing season of about 182 days.
Planting calendar for Grafton
Dates are counted from the average last spring frost (April 23) 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: Feb 26 – Mar 12 Transplant outdoors: Apr 30 – May 7 |
| Peppers | Start seeds indoors: Feb 12 – Feb 26 Transplant outdoors: May 7 – May 14 |
| Eggplant | Start seeds indoors: Feb 12 – Feb 26 Transplant outdoors: May 7 – May 14 |
| Broccoli | Start seeds indoors: Feb 12 – Feb 26 Transplant outdoors: Mar 26 – Apr 9 |
| Cabbage | Start seeds indoors: Feb 12 – Feb 26 Transplant outdoors: Mar 26 – Apr 9 |
| Onions (sets) | Plant outdoors: Mar 26 – Apr 9 |
| Peas | Sow outdoors: Mar 12 – Mar 26 |
| Spinach | Sow outdoors: Mar 12 – Mar 26 |
| Lettuce | Sow outdoors: Mar 26 – Apr 9 |
| Carrots | Sow outdoors: Mar 26 – Apr 9 |
| Potatoes | Plant outdoors: Mar 26 – Apr 9 |
| Beans | Sow outdoors: Apr 30 – May 7 |
| Sweet corn | Sow outdoors: Apr 30 – May 7 |
| Cucumbers | Sow outdoors: Apr 30 – May 7 |
| Squash & zucchini | Sow outdoors: Apr 30 – May 7 |
| Basil | Start seeds indoors: Mar 12 – Mar 26 Transplant outdoors: Apr 30 – May 7 |
Fall garden: cool-season crops like lettuce, spinach and kale can be sown again around Aug 29 (8 weeks before the average first fall frost on Oct 24).
Useful for zone 6a 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 10 | Apr 23 | May 9 |
| First 32°F frost in fall is before | Nov 5 | Oct 24 | Oct 8 |
How to read it: in spring there is a 10% chance of a frost after May 9, so that is a safe date for tender plants. In fall there is a 10% chance of frost before October 8. A hard freeze (28°F) usually ends around April 11.
Hardiness zone by ZIP code in Grafton
- 53024 zone 6a
Nearby cities
- Cedarburg zone 5b, last frost Apr 23
- Port Washington zone 5b, last frost Apr 27
- Mequon zone 5b, last frost May 6
- Brown Deer zone 6a, last frost Apr 26
- Germantown zone 5b, last frost May 6
- Glendale zone 6a, last frost Apr 26
- Whitefish Bay zone 6a, last frost Apr 26
- Menomonee Falls zone 5b, last frost May 6
Questions
What growing zone is Grafton, WI?
Grafton is in USDA Plant Hardiness Zone 6a (average extreme winter low -10°F to -5°F), according to the USDA 2023 map.
When is the last frost in Grafton?
The average last spring frost (32°F) in Grafton is April 23. There is still a 10% chance of frost until May 9.
When can I plant tomatoes in Grafton?
Transplant tomatoes outdoors 1–2 weeks after the average last frost: around Apr 30 – May 7. Start seeds indoors 6–8 weeks before the last frost.
Frost dates: NOAA U.S. Climate Normals 1991–2020, station Grafton Wwtp, WI (USC00473198), 1.3 km (0.8 mi) from the city center, elevation 226 m, based on 12 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.