Fortine, MT frost dates
Last spring frostMay 16median date
First fall frostSep 18median date
Growing season125 daysfrost-free
Hardiness zone5aZone 5a
How Fortine compares
- In 8 years out of 10, the last spring frost in Fortine falls between May 3 and June 3, a 31-day window. The first fall frost falls between September 1 and October 5.
- The median last frost is 3 days earlier than the Montana median of May 19.
- Its 125-day growing season is longer than 47% of the 325 Montana places with a regular frost season (state median 125 days).
- The last frost is 13 days later than the zone 5a median of May 3. Hardiness zones measure winter cold, not season length, so use these dates rather than a zone 5a chart.
- The weather station records an average of 183 nights a year at or below 32°F.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | May 3 |
| 50% (median) | May 16 |
| 10% (safe for tender plants) | June 3 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | September 1 |
| 50% (median) | September 18 |
| 90% (late) | October 5 |
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 Fortine, MT
Fortine, MT frost dates — last frost May 16, first frost Sep 18, zone 5a. whenisthelastfrost.com
Crop
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Start indoors: Feb 21 to Mar 7Transplant outside: Apr 18 to May 2
Start indoors: Mar 7 to Mar 21Transplant outside: May 30 to Jun 13
Start indoors: Mar 7 to Mar 21Transplant outside: May 30 to Jun 13
Start indoors: Mar 21 to Apr 4Transplant outside: May 23 to Jun 6
Start indoors: Mar 21 to Apr 4Transplant outside: Apr 25 to May 9Sow outdoors: Apr 18 to May 23Plant for fall: Jul 24 to Aug 21
Start indoors: Mar 21 to Apr 4Transplant outside: Apr 18 to May 2Sow outdoors: Apr 18 to May 2Plant for fall: Jul 10 to Jul 31
Start indoors: Mar 21 to Apr 4Transplant outside: May 2 to May 16Plant for fall: Jun 12 to Jul 3
Start indoors: Mar 21 to Apr 4Transplant outside: Apr 25 to May 9Plant for fall: Jun 12 to Jul 3
Start indoors: Mar 21 to Apr 4Transplant outside: May 2 to May 16Plant for fall: Jun 12 to Jul 3
Start indoors: Apr 4 to Apr 18Transplant outside: Jun 6 to Jun 20Sow outdoors: Jun 6 to Jun 20
Start indoors: Apr 4 to Apr 18Transplant outside: May 23 to Jun 6
Sow outdoors: Apr 4 to Apr 25Plant for fall: Jun 26 to Jul 17
Sow outdoors: Apr 4 to Apr 25Plant for fall: Jul 24 to Aug 14
Sow outdoors: Apr 11 to May 23Plant for fall: Aug 7 to Aug 28
Start indoors: Apr 18 to Apr 25Transplant outside: May 30 to Jun 6Sow outdoors: May 23 to Jun 6Plant for fall: Jul 3 to Jul 17
Start indoors: Apr 18 to Apr 25Sow outdoors: May 23 to Jun 6Plant for fall: Jul 10 to Jul 24
Start indoors: Apr 18 to Apr 25Sow outdoors: May 23 to Jun 6
Start indoors: Apr 18 to Apr 25Transplant outside: May 30 to Jun 13
Sow outdoors: Apr 25 to May 23Plant for fall: Jun 26 to Jul 10
Sow outdoors: Apr 25 to May 23Plant for fall: Jul 10 to Jul 24
Sow outdoors: Apr 25 to May 16
Sow outdoors: May 2 to May 30Plant for fall: Jul 10 to Jul 24
Sow outdoors: May 2 to May 23Plant for fall: Jul 24 to Aug 14
Sow outdoors: May 23 to Jun 13Plant for fall: Jul 3 to Jul 17
Sow outdoors: May 23 to Jun 6
Transplant outside: May 30 to Jun 20
Plant for fall: Sep 4 to Oct 9
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Fortine, MT
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Feb 21 – Mar 7 | Apr 18 – May 2 | — | — |
| Peppers | Mar 7 – Mar 21 | May 30 – Jun 13 | — | — |
| Eggplant | Mar 7 – Mar 21 | May 30 – Jun 13 | — | — |
| Tomatoes | Mar 21 – Apr 4 | May 23 – Jun 6 | — | — |
| Lettuce | Mar 21 – Apr 4 | Apr 25 – May 9 | Apr 18 – May 23 | Jul 24 – Aug 21 |
| Kale | Mar 21 – Apr 4 | Apr 18 – May 2 | Apr 18 – May 2 | Jul 10 – Jul 31 |
| Broccoli | Mar 21 – Apr 4 | May 2 – May 16 | — | Jun 12 – Jul 3 |
| Cabbage | Mar 21 – Apr 4 | Apr 25 – May 9 | — | Jun 12 – Jul 3 |
| Cauliflower | Mar 21 – Apr 4 | May 2 – May 16 | — | Jun 12 – Jul 3 |
| Okra | Apr 4 – Apr 18 | Jun 6 – Jun 20 | Jun 6 – Jun 20 | — |
| Basil | Apr 4 – Apr 18 | May 23 – Jun 6 | — | — |
| Peas | — | — | Apr 4 – Apr 25 | Jun 26 – Jul 17 |
| Spinach | — | — | Apr 4 – Apr 25 | Jul 24 – Aug 14 |
| Radishes | — | — | Apr 11 – May 23 | Aug 7 – Aug 28 |
| Cucumbers | Apr 18 – Apr 25 | May 30 – Jun 6 | May 23 – Jun 6 | Jul 3 – Jul 17 |
| Zucchini & Summer Squash | Apr 18 – Apr 25 | — | May 23 – Jun 6 | Jul 10 – Jul 24 |
| Winter Squash & Pumpkins | Apr 18 – Apr 25 | — | May 23 – Jun 6 | — |
| Melons & Watermelon | Apr 18 – Apr 25 | May 30 – Jun 13 | — | — |
| Carrots | — | — | Apr 25 – May 23 | Jun 26 – Jul 10 |
| Beets | — | — | Apr 25 – May 23 | Jul 10 – Jul 24 |
| Potatoes | — | — | Apr 25 – May 16 | — |
| Swiss Chard | — | — | May 2 – May 30 | Jul 10 – Jul 24 |
| Cilantro | — | — | May 2 – May 23 | Jul 24 – Aug 14 |
| Green Beans | — | — | May 23 – Jun 13 | Jul 3 – Jul 17 |
| Sweet Corn | — | — | May 23 – Jun 6 | — |
| Sweet Potatoes | — | May 30 – Jun 20 | — | — |
| Garlic | — | — | — | Sep 4 – Oct 9 |
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 Fortine 1 N, MT weather station, 3 km away (elevation 2,999 ft (914 m)).
Frost dates near Fortine
- Trego May 16 · Sep 18
- Stryker May 16 · Sep 18
- Eureka May 11 · Sep 27
- Rexford May 11 · Sep 27
- Olney frost any month
- Polebridge frost any month
- Whitefish May 16 · Sep 25
- Libby May 10 · Sep 26
- Columbia Falls May 31 · Sep 10
- Coram May 18 · Sep 20
Frequently asked questions
When is the last frost in Fortine, MT?
The median last spring frost in Fortine, MT is May 16. 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 Fortine, MT?
The median first fall frost is September 18, with about a 10% chance of frost before September 1.
How long is the growing season in Fortine, MT?
About 125 days between the median last spring frost and first fall frost.
What planting zone is Fortine, MT?
Fortine, MT is in USDA hardiness zone 5a.