Superior, WI planting zone & frost dates
Superior is in USDA hardiness zone 5a. The last spring frost usually comes around May 6 and the first fall frost around October 9, for a growing season of about 154 days.
Planting calendar for Superior
Dates are counted from the average last spring frost (May 6) 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 11 – Mar 25 Transplant outdoors: May 13 – May 20 |
| Peppers | Start seeds indoors: Feb 25 – Mar 11 Transplant outdoors: May 20 – May 27 |
| Eggplant | Start seeds indoors: Feb 25 – Mar 11 Transplant outdoors: May 20 – May 27 |
| Broccoli | Start seeds indoors: Feb 25 – Mar 11 Transplant outdoors: Apr 8 – Apr 22 |
| Cabbage | Start seeds indoors: Feb 25 – Mar 11 Transplant outdoors: Apr 8 – Apr 22 |
| Onions (sets) | Plant outdoors: Apr 8 – Apr 22 |
| Peas | Sow outdoors: Mar 25 – Apr 8 |
| Spinach | Sow outdoors: Mar 25 – Apr 8 |
| Lettuce | Sow outdoors: Apr 8 – Apr 22 |
| Carrots | Sow outdoors: Apr 8 – Apr 22 |
| Potatoes | Plant outdoors: Apr 8 – Apr 22 |
| Beans | Sow outdoors: May 13 – May 20 |
| Sweet corn | Sow outdoors: May 13 – May 20 |
| Cucumbers | Sow outdoors: May 13 – May 20 |
| Squash & zucchini | Sow outdoors: May 13 – May 20 |
| Basil | Start seeds indoors: Mar 25 – Apr 8 Transplant outdoors: May 13 – May 20 |
Fall garden: cool-season crops like lettuce, spinach and kale can be sown again around Aug 14 (8 weeks before the average first fall frost on Oct 9).
Useful for zone 5a 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 24 | May 6 | May 25 |
| First 32°F frost in fall is before | Oct 24 | Oct 9 | Sep 24 |
How to read it: in spring there is a 10% chance of a frost after May 25, so that is a safe date for tender plants. In fall there is a 10% chance of frost before September 24. A hard freeze (28°F) usually ends around April 24.
Hardiness zone by ZIP code in Superior
- 54880 zone 4b
Nearby cities
- Menomonie zone 4b, last frost May 9
- Hudson zone 5a, last frost Apr 22
- Chippewa Falls zone 4b, last frost May 8
- River Falls zone 4b, last frost May 11
- Eau Claire zone 4b, last frost Apr 24
- Marshfield zone 4b, last frost May 5
- Onalaska zone 5a, last frost Apr 23
- North La Crosse zone 5a, last frost Apr 23
Questions
What growing zone is Superior, WI?
Superior is in USDA Plant Hardiness Zone 5a (average extreme winter low -20°F to -15°F), according to the USDA 2023 map. Some ZIP codes of the city fall in zone 4b.
When is the last frost in Superior?
The average last spring frost (32°F) in Superior is May 6. There is still a 10% chance of frost until May 25.
When can I plant tomatoes in Superior?
Transplant tomatoes outdoors 1–2 weeks after the average last frost: around May 13 – May 20. Start seeds indoors 6–8 weeks before the last frost.
Frost dates: NOAA U.S. Climate Normals 1991–2020, station Superior, WI (USC00478349), 2.5 km (1.6 mi) from the city center, elevation 185 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.