Frost dates for 59404 — Great Falls, MT
Last spring frostMay 19median date
First fall frostSep 24median date
Growing season128 daysfrost-free
Hardiness zone4bZone 4b
How Great Falls compares
- In 8 years out of 10, the last spring frost in Great Falls falls between May 7 and June 2, a 26-day window. The first fall frost falls between September 9 and October 5.
- The median last frost is the same as the Montana median of May 19.
- Its 128-day growing season is longer than 55% of the 325 Montana places with a regular frost season (state median 125 days).
- The last frost is 11 days later than the zone 4b median of May 8. Hardiness zones measure winter cold, not season length, so use these dates rather than a zone 4b chart.
- The weather station records an average of 168 nights a year at or below 32°F.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | May 7 |
| 50% (median) | May 19 |
| 10% (safe for tender plants) | June 2 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | September 9 |
| 50% (median) | September 24 |
| 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 Great Falls, MT
Frost dates for 59404 — Great Falls, MT — last frost May 19, first frost Sep 24, zone 4b. whenisthelastfrost.com
Crop
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Start indoors: Feb 24 to Mar 10Transplant outside: Apr 21 to May 5
Start indoors: Mar 10 to Mar 24Transplant outside: Jun 2 to Jun 16
Start indoors: Mar 10 to Mar 24Transplant outside: Jun 2 to Jun 16
Start indoors: Mar 24 to Apr 7Transplant outside: May 26 to Jun 9
Start indoors: Mar 24 to Apr 7Transplant outside: Apr 28 to May 12Sow outdoors: Apr 21 to May 26Plant for fall: Jul 30 to Aug 27
Start indoors: Mar 24 to Apr 7Transplant outside: Apr 21 to May 5Sow outdoors: Apr 21 to May 5Plant for fall: Jul 16 to Aug 6
Start indoors: Mar 24 to Apr 7Transplant outside: May 5 to May 19Plant for fall: Jun 18 to Jul 9
Start indoors: Mar 24 to Apr 7Transplant outside: Apr 28 to May 12Plant for fall: Jun 18 to Jul 9
Start indoors: Mar 24 to Apr 7Transplant outside: May 5 to May 19Plant for fall: Jun 18 to Jul 9
Start indoors: Apr 7 to Apr 21Transplant outside: Jun 9 to Jun 23Sow outdoors: Jun 9 to Jun 23
Start indoors: Apr 7 to Apr 21Transplant outside: May 26 to Jun 9
Sow outdoors: Apr 7 to Apr 28Plant for fall: Jul 2 to Jul 23
Sow outdoors: Apr 7 to Apr 28Plant for fall: Jul 30 to Aug 20
Sow outdoors: Apr 14 to May 26Plant for fall: Aug 13 to Sep 3
Start indoors: Apr 21 to Apr 28Transplant outside: Jun 2 to Jun 9Sow outdoors: May 26 to Jun 9Plant for fall: Jul 9 to Jul 23
Start indoors: Apr 21 to Apr 28Sow outdoors: May 26 to Jun 9Plant for fall: Jul 16 to Jul 30
Start indoors: Apr 21 to Apr 28Sow outdoors: May 26 to Jun 9
Start indoors: Apr 21 to Apr 28Transplant outside: Jun 2 to Jun 16
Sow outdoors: Apr 28 to May 26Plant for fall: Jul 2 to Jul 16
Sow outdoors: Apr 28 to May 26Plant for fall: Jul 16 to Jul 30
Sow outdoors: Apr 28 to May 19
Sow outdoors: May 5 to Jun 2Plant for fall: Jul 16 to Jul 30
Sow outdoors: May 5 to May 26Plant for fall: Jul 30 to Aug 20
Sow outdoors: May 26 to Jun 16Plant for fall: Jul 9 to Jul 23
Sow outdoors: May 26 to Jun 9
Transplant outside: Jun 2 to Jun 23
Plant for fall: Sep 10 to Oct 15
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Great Falls, MT
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Feb 24 – Mar 10 | Apr 21 – May 5 | — | — |
| Peppers | Mar 10 – Mar 24 | Jun 2 – Jun 16 | — | — |
| Eggplant | Mar 10 – Mar 24 | Jun 2 – Jun 16 | — | — |
| Tomatoes | Mar 24 – Apr 7 | May 26 – Jun 9 | — | — |
| Lettuce | Mar 24 – Apr 7 | Apr 28 – May 12 | Apr 21 – May 26 | Jul 30 – Aug 27 |
| Kale | Mar 24 – Apr 7 | Apr 21 – May 5 | Apr 21 – May 5 | Jul 16 – Aug 6 |
| Broccoli | Mar 24 – Apr 7 | May 5 – May 19 | — | Jun 18 – Jul 9 |
| Cabbage | Mar 24 – Apr 7 | Apr 28 – May 12 | — | Jun 18 – Jul 9 |
| Cauliflower | Mar 24 – Apr 7 | May 5 – May 19 | — | Jun 18 – Jul 9 |
| Okra | Apr 7 – Apr 21 | Jun 9 – Jun 23 | Jun 9 – Jun 23 | — |
| Basil | Apr 7 – Apr 21 | May 26 – Jun 9 | — | — |
| Peas | — | — | Apr 7 – Apr 28 | Jul 2 – Jul 23 |
| Spinach | — | — | Apr 7 – Apr 28 | Jul 30 – Aug 20 |
| Radishes | — | — | Apr 14 – May 26 | Aug 13 – Sep 3 |
| Cucumbers | Apr 21 – Apr 28 | Jun 2 – Jun 9 | May 26 – Jun 9 | Jul 9 – Jul 23 |
| Zucchini & Summer Squash | Apr 21 – Apr 28 | — | May 26 – Jun 9 | Jul 16 – Jul 30 |
| Winter Squash & Pumpkins | Apr 21 – Apr 28 | — | May 26 – Jun 9 | — |
| Melons & Watermelon | Apr 21 – Apr 28 | Jun 2 – Jun 16 | — | — |
| Carrots | — | — | Apr 28 – May 26 | Jul 2 – Jul 16 |
| Beets | — | — | Apr 28 – May 26 | Jul 16 – Jul 30 |
| Potatoes | — | — | Apr 28 – May 19 | — |
| Swiss Chard | — | — | May 5 – Jun 2 | Jul 16 – Jul 30 |
| Cilantro | — | — | May 5 – May 26 | Jul 30 – Aug 20 |
| Green Beans | — | — | May 26 – Jun 16 | Jul 9 – Jul 23 |
| Sweet Corn | — | — | May 26 – Jun 9 | — |
| Sweet Potatoes | — | Jun 2 – Jun 23 | — | — |
| Garlic | — | — | — | Sep 10 – Oct 15 |
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 Great Falls Intl Ap, MT weather station, 5 km away (elevation 3,665 ft (1,117 m)).
ZIP codes in Great Falls: 59401 59403 59404 59405 59406
Frost dates near Great Falls
- Malmstrom Afb May 6 · Oct 1
- Black Eagle May 6 · Oct 1
- Sand Coulee May 6 · Oct 1
- Vaughn Jun 2 · Sep 10
- Floweree May 23 · Sep 23
- Ulm May 21 · Sep 19
- Stockett May 6 · Oct 1
- Sun River Jun 2 · Sep 10
Frequently asked questions
When is the last frost in Great Falls, MT?
The median last spring frost in Great Falls, MT is May 19. There is still about a 10% chance of frost after June 2, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Great Falls, MT?
The median first fall frost is September 24, with about a 10% chance of frost before September 9.
How long is the growing season in Great Falls, MT?
About 128 days between the median last spring frost and first fall frost.
What planting zone is Great Falls, MT?
Great Falls, MT is in USDA hardiness zone 4b.