Superior, MT frost dates
Last spring frostMay 17median date
First fall frostSep 23median date
Growing season129 daysfrost-free
Hardiness zone6aZone 6a
How Superior compares
- In 8 years out of 10, the last spring frost in Superior falls between May 1 and June 8, a 38-day window. The first fall frost falls between September 6 and October 7.
- The median last frost is 2 days earlier than the Montana median of May 19.
- Its 129-day growing season is longer than 57% of the 325 Montana places with a regular frost season (state median 125 days).
- The last frost is 18 days later than the zone 6a median of Apr 29. Hardiness zones measure winter cold, not season length, so use these dates rather than a zone 6a chart.
- The weather station records an average of 161 nights a year at or below 32°F.
- Compared with Missoula, MT, 73 km away, the last frost here is 7 days later than there and the growing season is 15 days shorter.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | May 1 |
| 50% (median) | May 17 |
| 10% (safe for tender plants) | June 8 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | September 6 |
| 50% (median) | September 23 |
| 90% (late) | October 7 |
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, MT
Superior, MT frost dates — last frost May 17, first frost Sep 23, zone 6a. whenisthelastfrost.com
Crop
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Start indoors: Feb 22 to Mar 8Transplant outside: Apr 19 to May 3
Start indoors: Mar 8 to Mar 22Transplant outside: May 31 to Jun 14
Start indoors: Mar 8 to Mar 22Transplant outside: May 31 to Jun 14
Start indoors: Mar 22 to Apr 5Transplant outside: May 24 to Jun 7
Start indoors: Mar 22 to Apr 5Transplant outside: Apr 26 to May 10Sow outdoors: Apr 19 to May 24Plant for fall: Jul 29 to Aug 26
Start indoors: Mar 22 to Apr 5Transplant outside: Apr 19 to May 3Sow outdoors: Apr 19 to May 3Plant for fall: Jul 15 to Aug 5
Start indoors: Mar 22 to Apr 5Transplant outside: May 3 to May 17Plant for fall: Jun 17 to Jul 8
Start indoors: Mar 22 to Apr 5Transplant outside: Apr 26 to May 10Plant for fall: Jun 17 to Jul 8
Start indoors: Mar 22 to Apr 5Transplant outside: May 3 to May 17Plant for fall: Jun 17 to Jul 8
Start indoors: Apr 5 to Apr 19Transplant outside: Jun 7 to Jun 21Sow outdoors: Jun 7 to Jun 21
Start indoors: Apr 5 to Apr 19Transplant outside: May 24 to Jun 7
Sow outdoors: Apr 5 to Apr 26Plant for fall: Jul 1 to Jul 22
Sow outdoors: Apr 5 to Apr 26Plant for fall: Jul 29 to Aug 19
Sow outdoors: Apr 12 to May 24Plant for fall: Aug 12 to Sep 2
Start indoors: Apr 19 to Apr 26Transplant outside: May 31 to Jun 7Sow outdoors: May 24 to Jun 7Plant for fall: Jul 8 to Jul 22
Start indoors: Apr 19 to Apr 26Sow outdoors: May 24 to Jun 7Plant for fall: Jul 15 to Jul 29
Start indoors: Apr 19 to Apr 26Sow outdoors: May 24 to Jun 7
Start indoors: Apr 19 to Apr 26Transplant outside: May 31 to Jun 14
Sow outdoors: Apr 26 to May 24Plant for fall: Jul 1 to Jul 15
Sow outdoors: Apr 26 to May 24Plant for fall: Jul 15 to Jul 29
Sow outdoors: Apr 26 to May 17
Sow outdoors: May 3 to May 31Plant for fall: Jul 15 to Jul 29
Sow outdoors: May 3 to May 24Plant for fall: Jul 29 to Aug 19
Sow outdoors: May 24 to Jun 14Plant for fall: Jul 8 to Jul 22
Sow outdoors: May 24 to Jun 7
Transplant outside: May 31 to Jun 21
Plant for fall: Sep 9 to Oct 14
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Superior, MT
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Feb 22 – Mar 8 | Apr 19 – May 3 | — | — |
| Peppers | Mar 8 – Mar 22 | May 31 – Jun 14 | — | — |
| Eggplant | Mar 8 – Mar 22 | May 31 – Jun 14 | — | — |
| Tomatoes | Mar 22 – Apr 5 | May 24 – Jun 7 | — | — |
| Lettuce | Mar 22 – Apr 5 | Apr 26 – May 10 | Apr 19 – May 24 | Jul 29 – Aug 26 |
| Kale | Mar 22 – Apr 5 | Apr 19 – May 3 | Apr 19 – May 3 | Jul 15 – Aug 5 |
| Broccoli | Mar 22 – Apr 5 | May 3 – May 17 | — | Jun 17 – Jul 8 |
| Cabbage | Mar 22 – Apr 5 | Apr 26 – May 10 | — | Jun 17 – Jul 8 |
| Cauliflower | Mar 22 – Apr 5 | May 3 – May 17 | — | Jun 17 – Jul 8 |
| Okra | Apr 5 – Apr 19 | Jun 7 – Jun 21 | Jun 7 – Jun 21 | — |
| Basil | Apr 5 – Apr 19 | May 24 – Jun 7 | — | — |
| Peas | — | — | Apr 5 – Apr 26 | Jul 1 – Jul 22 |
| Spinach | — | — | Apr 5 – Apr 26 | Jul 29 – Aug 19 |
| Radishes | — | — | Apr 12 – May 24 | Aug 12 – Sep 2 |
| Cucumbers | Apr 19 – Apr 26 | May 31 – Jun 7 | May 24 – Jun 7 | Jul 8 – Jul 22 |
| Zucchini & Summer Squash | Apr 19 – Apr 26 | — | May 24 – Jun 7 | Jul 15 – Jul 29 |
| Winter Squash & Pumpkins | Apr 19 – Apr 26 | — | May 24 – Jun 7 | — |
| Melons & Watermelon | Apr 19 – Apr 26 | May 31 – Jun 14 | — | — |
| Carrots | — | — | Apr 26 – May 24 | Jul 1 – Jul 15 |
| Beets | — | — | Apr 26 – May 24 | Jul 15 – Jul 29 |
| Potatoes | — | — | Apr 26 – May 17 | — |
| Swiss Chard | — | — | May 3 – May 31 | Jul 15 – Jul 29 |
| Cilantro | — | — | May 3 – May 24 | Jul 29 – Aug 19 |
| Green Beans | — | — | May 24 – Jun 14 | Jul 8 – Jul 22 |
| Sweet Corn | — | — | May 24 – Jun 7 | — |
| Sweet Potatoes | — | May 31 – Jun 21 | — | — |
| Garlic | — | — | — | Sep 9 – Oct 14 |
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, MT weather station, 2 km away (elevation 2,710 ft (826 m)).
Frost dates near Superior
- Paradise May 17 · Sep 23
- Saint Regis frost any month
- Plains frost any month
- Alberton May 18 · Sep 25
- Huson May 18 · Sep 25
- De Borgia frost any month
- Haugan frost any month
- Dixon May 12 · Oct 2
- Frenchtown May 18 · Sep 25
- Hot Springs May 15 · Sep 28
Frequently asked questions
When is the last frost in Superior, MT?
The median last spring frost in Superior, MT is May 17. There is still about a 10% chance of frost after June 8, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Superior, MT?
The median first fall frost is September 23, with about a 10% chance of frost before September 6.
How long is the growing season in Superior, MT?
About 129 days between the median last spring frost and first fall frost.
What planting zone is Superior, MT?
Superior, MT is in USDA hardiness zone 6a.