Culbertson, MT frost dates
Last spring frostMay 21median date
First fall frostSep 20median date
Growing season122 daysfrost-free
Hardiness zone4aZone 4a
How Culbertson compares
- In 8 years out of 10, the last spring frost in Culbertson falls between May 8 and June 3, a 26-day window. The first fall frost falls between September 6 and September 30.
- The median last frost is 2 days later than the Montana median of May 19.
- Its 122-day growing season is longer than 38% of the 325 Montana places with a regular frost season (state median 125 days).
- The last frost is 9 days later than the zone 4a median of May 12. Hardiness zones measure winter cold, not season length, so use these dates rather than a zone 4a chart.
- The weather station records an average of 191 nights a year at or below 32°F.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | May 8 |
| 50% (median) | May 21 |
| 10% (safe for tender plants) | June 3 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | September 6 |
| 50% (median) | September 20 |
| 90% (late) | September 30 |
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 Culbertson, MT
Culbertson, MT frost dates — last frost May 21, first frost Sep 20, zone 4a. whenisthelastfrost.com
Crop
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Start indoors: Feb 26 to Mar 12Transplant outside: Apr 23 to May 7
Start indoors: Mar 12 to Mar 26Transplant outside: Jun 4 to Jun 18
Start indoors: Mar 12 to Mar 26Transplant outside: Jun 4 to Jun 18
Start indoors: Mar 26 to Apr 9Transplant outside: May 28 to Jun 11
Start indoors: Mar 26 to Apr 9Transplant outside: Apr 30 to May 14Sow outdoors: Apr 23 to May 28Plant for fall: Jul 26 to Aug 23
Start indoors: Mar 26 to Apr 9Transplant outside: Apr 23 to May 7Sow outdoors: Apr 23 to May 7Plant for fall: Jul 12 to Aug 2
Start indoors: Mar 26 to Apr 9Transplant outside: May 7 to May 21Plant for fall: Jun 14 to Jul 5
Start indoors: Mar 26 to Apr 9Transplant outside: Apr 30 to May 14Plant for fall: Jun 14 to Jul 5
Start indoors: Mar 26 to Apr 9Transplant outside: May 7 to May 21Plant for fall: Jun 14 to Jul 5
Start indoors: Apr 9 to Apr 23Transplant outside: Jun 11 to Jun 25Sow outdoors: Jun 11 to Jun 25
Start indoors: Apr 9 to Apr 23Transplant outside: May 28 to Jun 11
Sow outdoors: Apr 9 to Apr 30Plant for fall: Jun 28 to Jul 19
Sow outdoors: Apr 9 to Apr 30Plant for fall: Jul 26 to Aug 16
Sow outdoors: Apr 16 to May 28Plant for fall: Aug 9 to Aug 30
Start indoors: Apr 23 to Apr 30Transplant outside: Jun 4 to Jun 11Sow outdoors: May 28 to Jun 11Plant for fall: Jul 5 to Jul 19
Start indoors: Apr 23 to Apr 30Sow outdoors: May 28 to Jun 11Plant for fall: Jul 12 to Jul 26
Start indoors: Apr 23 to Apr 30Sow outdoors: May 28 to Jun 11
Start indoors: Apr 23 to Apr 30Transplant outside: Jun 4 to Jun 18
Sow outdoors: Apr 30 to May 28Plant for fall: Jun 28 to Jul 12
Sow outdoors: Apr 30 to May 28Plant for fall: Jul 12 to Jul 26
Sow outdoors: Apr 30 to May 21
Sow outdoors: May 7 to Jun 4Plant for fall: Jul 12 to Jul 26
Sow outdoors: May 7 to May 28Plant for fall: Jul 26 to Aug 16
Sow outdoors: May 28 to Jun 18Plant for fall: Jul 5 to Jul 19
Sow outdoors: May 28 to Jun 11
Transplant outside: Jun 4 to Jun 25
Plant for fall: Sep 6 to Oct 11
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Culbertson, MT
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Feb 26 – Mar 12 | Apr 23 – May 7 | — | — |
| Peppers | Mar 12 – Mar 26 | Jun 4 – Jun 18 | — | — |
| Eggplant | Mar 12 – Mar 26 | Jun 4 – Jun 18 | — | — |
| Tomatoes | Mar 26 – Apr 9 | May 28 – Jun 11 | — | — |
| Lettuce | Mar 26 – Apr 9 | Apr 30 – May 14 | Apr 23 – May 28 | Jul 26 – Aug 23 |
| Kale | Mar 26 – Apr 9 | Apr 23 – May 7 | Apr 23 – May 7 | Jul 12 – Aug 2 |
| Broccoli | Mar 26 – Apr 9 | May 7 – May 21 | — | Jun 14 – Jul 5 |
| Cabbage | Mar 26 – Apr 9 | Apr 30 – May 14 | — | Jun 14 – Jul 5 |
| Cauliflower | Mar 26 – Apr 9 | May 7 – May 21 | — | Jun 14 – Jul 5 |
| Okra | Apr 9 – Apr 23 | Jun 11 – Jun 25 | Jun 11 – Jun 25 | — |
| Basil | Apr 9 – Apr 23 | May 28 – Jun 11 | — | — |
| Peas | — | — | Apr 9 – Apr 30 | Jun 28 – Jul 19 |
| Spinach | — | — | Apr 9 – Apr 30 | Jul 26 – Aug 16 |
| Radishes | — | — | Apr 16 – May 28 | Aug 9 – Aug 30 |
| Cucumbers | Apr 23 – Apr 30 | Jun 4 – Jun 11 | May 28 – Jun 11 | Jul 5 – Jul 19 |
| Zucchini & Summer Squash | Apr 23 – Apr 30 | — | May 28 – Jun 11 | Jul 12 – Jul 26 |
| Winter Squash & Pumpkins | Apr 23 – Apr 30 | — | May 28 – Jun 11 | — |
| Melons & Watermelon | Apr 23 – Apr 30 | Jun 4 – Jun 18 | — | — |
| Carrots | — | — | Apr 30 – May 28 | Jun 28 – Jul 12 |
| Beets | — | — | Apr 30 – May 28 | Jul 12 – Jul 26 |
| Potatoes | — | — | Apr 30 – May 21 | — |
| Swiss Chard | — | — | May 7 – Jun 4 | Jul 12 – Jul 26 |
| Cilantro | — | — | May 7 – May 28 | Jul 26 – Aug 16 |
| Green Beans | — | — | May 28 – Jun 18 | Jul 5 – Jul 19 |
| Sweet Corn | — | — | May 28 – Jun 11 | — |
| Sweet Potatoes | — | Jun 4 – Jun 25 | — | — |
| Garlic | — | — | — | Sep 6 – Oct 11 |
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 Culbertson, MT weather station, about 1 km away (elevation 1,939 ft (591 m)).
Frost dates near Culbertson
- Froid May 16 · Sep 18
- Bainville May 21 · Sep 20
- Brockton May 24 · Sep 14
- Homestead May 16 · Sep 18
- Fairview May 11 · Sep 27
- Medicine Lake May 16 · Sep 18
- Lambert May 11 · Sep 27
- Reserve May 16 · Sep 18
- Poplar May 24 · Sep 14
- Dagmar May 16 · Sep 18
Frequently asked questions
When is the last frost in Culbertson, MT?
The median last spring frost in Culbertson, MT is May 21. There is still about a 10% chance of frost after June 3, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Culbertson, MT?
The median first fall frost is September 20, with about a 10% chance of frost before September 6.
How long is the growing season in Culbertson, MT?
About 122 days between the median last spring frost and first fall frost.
What planting zone is Culbertson, MT?
Culbertson, MT is in USDA hardiness zone 4a.