Cohagen, MT frost dates
Last spring frostMay 25median date
First fall frostSep 14median date
Growing season112 daysfrost-free
Hardiness zone4aZone 4a
How Cohagen compares
- In 8 years out of 10, the last spring frost in Cohagen falls between May 12 and June 9, a 28-day window. The first fall frost falls between August 31 and September 26.
- The median last frost is 6 days later than the Montana median of May 19.
- Its 112-day growing season is longer than 23% of the 325 Montana places with a regular frost season (state median 125 days).
- The last frost is 13 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 185 nights a year at or below 32°F.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | May 12 |
| 50% (median) | May 25 |
| 10% (safe for tender plants) | June 9 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | August 31 |
| 50% (median) | September 14 |
| 90% (late) | September 26 |
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 Cohagen, MT
Cohagen, MT frost dates — last frost May 25, first frost Sep 14, zone 4a. whenisthelastfrost.com
Crop
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Start indoors: Mar 2 to Mar 16Transplant outside: Apr 27 to May 11
Start indoors: Mar 16 to Mar 30Transplant outside: Jun 8 to Jun 22
Start indoors: Mar 16 to Mar 30Transplant outside: Jun 8 to Jun 22
Start indoors: Mar 30 to Apr 13Transplant outside: Jun 1 to Jun 15
Start indoors: Mar 30 to Apr 13Transplant outside: May 4 to May 18Sow outdoors: Apr 27 to Jun 1Plant for fall: Jul 20 to Aug 17
Start indoors: Mar 30 to Apr 13Transplant outside: Apr 27 to May 11Sow outdoors: Apr 27 to May 11Plant for fall: Jul 6 to Jul 27
Start indoors: Mar 30 to Apr 13Transplant outside: May 11 to May 25
Start indoors: Mar 30 to Apr 13Transplant outside: May 4 to May 18
Start indoors: Mar 30 to Apr 13Transplant outside: May 11 to May 25
Start indoors: Apr 13 to Apr 27Transplant outside: Jun 15 to Jun 29Sow outdoors: Jun 15 to Jun 29
Start indoors: Apr 13 to Apr 27Transplant outside: Jun 1 to Jun 15
Sow outdoors: Apr 13 to May 4Plant for fall: Jun 22 to Jul 13
Sow outdoors: Apr 13 to May 4Plant for fall: Jul 20 to Aug 10
Sow outdoors: Apr 20 to Jun 1Plant for fall: Aug 3 to Aug 24
Start indoors: Apr 27 to May 4Transplant outside: Jun 8 to Jun 15Sow outdoors: Jun 1 to Jun 15
Start indoors: Apr 27 to May 4Sow outdoors: Jun 1 to Jun 15Plant for fall: Jul 6 to Jul 20
Start indoors: Apr 27 to May 4Sow outdoors: Jun 1 to Jun 15
Start indoors: Apr 27 to May 4Transplant outside: Jun 8 to Jun 22
Sow outdoors: May 4 to Jun 1Plant for fall: Jun 22 to Jul 6
Sow outdoors: May 4 to Jun 1Plant for fall: Jul 6 to Jul 20
Sow outdoors: May 4 to May 25
Sow outdoors: May 11 to Jun 8Plant for fall: Jul 6 to Jul 20
Sow outdoors: May 11 to Jun 1Plant for fall: Jul 20 to Aug 10
Sow outdoors: Jun 1 to Jun 22
Sow outdoors: Jun 1 to Jun 15
Transplant outside: Jun 8 to Jun 29
Plant for fall: Aug 31 to Oct 5
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Cohagen, MT
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Mar 2 – Mar 16 | Apr 27 – May 11 | — | — |
| Peppers | Mar 16 – Mar 30 | Jun 8 – Jun 22 | — | — |
| Eggplant | Mar 16 – Mar 30 | Jun 8 – Jun 22 | — | — |
| Tomatoes | Mar 30 – Apr 13 | Jun 1 – Jun 15 | — | — |
| Lettuce | Mar 30 – Apr 13 | May 4 – May 18 | Apr 27 – Jun 1 | Jul 20 – Aug 17 |
| Kale | Mar 30 – Apr 13 | Apr 27 – May 11 | Apr 27 – May 11 | Jul 6 – Jul 27 |
| Broccoli | Mar 30 – Apr 13 | May 11 – May 25 | — | — |
| Cabbage | Mar 30 – Apr 13 | May 4 – May 18 | — | — |
| Cauliflower | Mar 30 – Apr 13 | May 11 – May 25 | — | — |
| Okra | Apr 13 – Apr 27 | Jun 15 – Jun 29 | Jun 15 – Jun 29 | — |
| Basil | Apr 13 – Apr 27 | Jun 1 – Jun 15 | — | — |
| Peas | — | — | Apr 13 – May 4 | Jun 22 – Jul 13 |
| Spinach | — | — | Apr 13 – May 4 | Jul 20 – Aug 10 |
| Radishes | — | — | Apr 20 – Jun 1 | Aug 3 – Aug 24 |
| Cucumbers | Apr 27 – May 4 | Jun 8 – Jun 15 | Jun 1 – Jun 15 | — |
| Zucchini & Summer Squash | Apr 27 – May 4 | — | Jun 1 – Jun 15 | Jul 6 – Jul 20 |
| Winter Squash & Pumpkins Warning: Your frost-free season is about 112 days, which is tight for winter squash & pumpkins (100+ days). Choose early varieties and use transplants or row covers. | Apr 27 – May 4 | — | Jun 1 – Jun 15 | — |
| Melons & Watermelon | Apr 27 – May 4 | Jun 8 – Jun 22 | — | — |
| Carrots | — | — | May 4 – Jun 1 | Jun 22 – Jul 6 |
| Beets | — | — | May 4 – Jun 1 | Jul 6 – Jul 20 |
| Potatoes | — | — | May 4 – May 25 | — |
| Swiss Chard | — | — | May 11 – Jun 8 | Jul 6 – Jul 20 |
| Cilantro | — | — | May 11 – Jun 1 | Jul 20 – Aug 10 |
| Green Beans | — | — | Jun 1 – Jun 22 | — |
| Sweet Corn | — | — | Jun 1 – Jun 15 | — |
| Sweet Potatoes Warning: Your frost-free season is about 112 days, which is tight for sweet potatoes (100+ days). Choose early varieties and use transplants or row covers. | — | Jun 8 – Jun 29 | — | — |
| Garlic | — | — | — | Aug 31 – Oct 5 |
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 Cohagen, MT weather station, 12 km away (elevation 2,720 ft (829 m)).
Frost dates near Cohagen
- Jordan May 21 · Sep 18
- Angela May 15 · Sep 25
- Brockway May 20 · Sep 19
- Brusett May 18 · Sep 20
- Circle May 17 · Sep 22
- Sand Springs May 5 · Oct 4
- Rosebud May 9 · Sep 29
- Kinsey May 8 · Sep 30
- Ingomar May 21 · Sep 19
- Terry May 12 · Sep 28
Frequently asked questions
When is the last frost in Cohagen, MT?
The median last spring frost in Cohagen, MT is May 25. There is still about a 10% chance of frost after June 9, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Cohagen, MT?
The median first fall frost is September 14, with about a 10% chance of frost before August 31.
How long is the growing season in Cohagen, MT?
About 112 days between the median last spring frost and first fall frost.
What planting zone is Cohagen, MT?
Cohagen, MT is in USDA hardiness zone 4a.