Superior, WI frost dates
Last spring frostMay 6median date
First fall frostOct 9median date
Growing season156 daysfrost-free
Hardiness zone4bZone 4b
How Superior compares
- In 8 years out of 10, the last spring frost in Superior falls between April 24 and May 25, a 31-day window. The first fall frost falls between September 24 and October 24.
- The median last frost is 1 day later than the Wisconsin median of May 5.
- Its 156-day growing season is longer than 55% of the 749 Wisconsin places with a regular frost season (state median 155 days).
- The last frost is typical for zone 4b, where the median is May 8.
- The weather station records an average of 161 nights a year at or below 32°F.
- Compared with Duluth, MN, 10 km away, the last frost here is 8 days earlier than there and the growing season is 5 days longer.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | April 24 |
| 50% (median) | May 6 |
| 10% (safe for tender plants) | May 25 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | September 24 |
| 50% (median) | October 9 |
| 90% (late) | October 24 |
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 Superior, WI
Superior, WI frost dates — last frost May 6, first frost Oct 9, zone 4b. whenisthelastfrost.com
Crop
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Start indoors: Feb 11 to Feb 25Transplant outside: Apr 8 to Apr 22
Start indoors: Feb 25 to Mar 11Transplant outside: May 20 to Jun 3
Start indoors: Feb 25 to Mar 11Transplant outside: May 20 to Jun 3
Start indoors: Mar 11 to Mar 25Transplant outside: May 13 to May 27
Start indoors: Mar 11 to Mar 25Transplant outside: Apr 15 to Apr 29Sow outdoors: Apr 8 to May 13Plant for fall: Aug 14 to Sep 11
Start indoors: Mar 11 to Mar 25Transplant outside: Apr 8 to Apr 22Sow outdoors: Apr 8 to Apr 22Plant for fall: Jul 31 to Aug 21
Start indoors: Mar 11 to Mar 25Transplant outside: Apr 22 to May 6Plant for fall: Jul 3 to Jul 24
Start indoors: Mar 11 to Mar 25Transplant outside: Apr 15 to Apr 29Plant for fall: Jul 3 to Jul 24
Start indoors: Mar 11 to Mar 25Transplant outside: Apr 22 to May 6Plant for fall: Jul 3 to Jul 24
Start indoors: Mar 25 to Apr 8Transplant outside: May 27 to Jun 10Sow outdoors: May 27 to Jun 10
Start indoors: Mar 25 to Apr 8Transplant outside: May 13 to May 27
Sow outdoors: Mar 25 to Apr 15Plant for fall: Jul 17 to Aug 7
Sow outdoors: Mar 25 to Apr 15Plant for fall: Aug 14 to Sep 4
Sow outdoors: Apr 1 to May 13Plant for fall: Aug 28 to Sep 18
Start indoors: Apr 8 to Apr 15Transplant outside: May 20 to May 27Sow outdoors: May 13 to May 27Plant for fall: Jul 24 to Aug 7
Start indoors: Apr 8 to Apr 15Sow outdoors: May 13 to May 27Plant for fall: Jul 31 to Aug 14
Start indoors: Apr 8 to Apr 15Sow outdoors: May 13 to May 27
Start indoors: Apr 8 to Apr 15Transplant outside: May 20 to Jun 3
Sow outdoors: Apr 15 to May 13Plant for fall: Jul 17 to Jul 31
Sow outdoors: Apr 15 to May 13Plant for fall: Jul 31 to Aug 14
Sow outdoors: Apr 15 to May 6
Sow outdoors: Apr 22 to May 20Plant for fall: Jul 31 to Aug 14
Sow outdoors: Apr 22 to May 13Plant for fall: Aug 14 to Sep 4
Sow outdoors: May 13 to Jun 3Plant for fall: Jul 24 to Aug 7
Sow outdoors: May 13 to May 27
Transplant outside: May 20 to Jun 10
Plant for fall: Sep 25 to Oct 30
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Superior, WI
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Feb 11 – Feb 25 | Apr 8 – Apr 22 | — | — |
| Peppers | Feb 25 – Mar 11 | May 20 – Jun 3 | — | — |
| Eggplant | Feb 25 – Mar 11 | May 20 – Jun 3 | — | — |
| Tomatoes | Mar 11 – Mar 25 | May 13 – May 27 | — | — |
| Lettuce | Mar 11 – Mar 25 | Apr 15 – Apr 29 | Apr 8 – May 13 | Aug 14 – Sep 11 |
| Kale | Mar 11 – Mar 25 | Apr 8 – Apr 22 | Apr 8 – Apr 22 | Jul 31 – Aug 21 |
| Broccoli | Mar 11 – Mar 25 | Apr 22 – May 6 | — | Jul 3 – Jul 24 |
| Cabbage | Mar 11 – Mar 25 | Apr 15 – Apr 29 | — | Jul 3 – Jul 24 |
| Cauliflower | Mar 11 – Mar 25 | Apr 22 – May 6 | — | Jul 3 – Jul 24 |
| Okra | Mar 25 – Apr 8 | May 27 – Jun 10 | May 27 – Jun 10 | — |
| Basil | Mar 25 – Apr 8 | May 13 – May 27 | — | — |
| Peas | — | — | Mar 25 – Apr 15 | Jul 17 – Aug 7 |
| Spinach | — | — | Mar 25 – Apr 15 | Aug 14 – Sep 4 |
| Radishes | — | — | Apr 1 – May 13 | Aug 28 – Sep 18 |
| Cucumbers | Apr 8 – Apr 15 | May 20 – May 27 | May 13 – May 27 | Jul 24 – Aug 7 |
| Zucchini & Summer Squash | Apr 8 – Apr 15 | — | May 13 – May 27 | Jul 31 – Aug 14 |
| Winter Squash & Pumpkins | Apr 8 – Apr 15 | — | May 13 – May 27 | — |
| Melons & Watermelon | Apr 8 – Apr 15 | May 20 – Jun 3 | — | — |
| Carrots | — | — | Apr 15 – May 13 | Jul 17 – Jul 31 |
| Beets | — | — | Apr 15 – May 13 | Jul 31 – Aug 14 |
| Potatoes | — | — | Apr 15 – May 6 | — |
| Swiss Chard | — | — | Apr 22 – May 20 | Jul 31 – Aug 14 |
| Cilantro | — | — | Apr 22 – May 13 | Aug 14 – Sep 4 |
| Green Beans | — | — | May 13 – Jun 3 | Jul 24 – Aug 7 |
| Sweet Corn | — | — | May 13 – May 27 | — |
| Sweet Potatoes | — | May 20 – Jun 10 | — | — |
| Garlic | — | — | — | Sep 25 – Oct 30 |
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 Superior, WI weather station, 3 km away (elevation 607 ft (185 m)).
Frost dates near Superior
- South Range May 18 · Oct 3
- Foxboro May 18 · Oct 3
- Poplar May 24 · Sep 26
- Hawthorne May 12 · Oct 2
- Maple May 24 · Sep 26
- Lake Nebagamon May 24 · Sep 26
- Solon Springs May 12 · Oct 2
- Brule May 24 · Sep 26
- Iron River May 24 · Sep 26
- Port Wing May 31 · Oct 2
Frequently asked questions
When is the last frost in Superior, WI?
The median last spring frost in Superior, WI is May 6. There is still about a 10% chance of frost after May 25, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Superior, WI?
The median first fall frost is October 9, with about a 10% chance of frost before September 24.
How long is the growing season in Superior, WI?
About 156 days between the median last spring frost and first fall frost.
What planting zone is Superior, WI?
Superior, WI is in USDA hardiness zone 4b.