Frost dates for 59401 — Great Falls, MT
Last spring frostMay 6median date
First fall frostOct 1median date
Growing season148 daysfrost-free
Hardiness zone4bZone 4b
How Great Falls compares
- In 8 years out of 10, the last spring frost in Great Falls falls between April 23 and May 19, a 26-day window. The first fall frost falls between September 17 and October 16.
- The median last frost is 13 days earlier than the Montana median of May 19.
- Its 148-day growing season is longer than 92% of the 325 Montana places with a regular frost season (state median 125 days).
- The last frost is typical for zone 4b, where the median is May 8.
- The weather station records an average of 143 nights a year at or below 32°F.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | April 23 |
| 50% (median) | May 6 |
| 10% (safe for tender plants) | May 19 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | September 17 |
| 50% (median) | October 1 |
| 90% (late) | October 16 |
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 59401 — Great Falls, MT — last frost May 6, first frost Oct 1, zone 4b. whenisthelastfrost.com
Crop
JFMAMJJASOND
Start indoors: Feb 11 to Feb 25Transplant outside: Apr 8 to Apr 22
Start indoors: Feb 25 to Mar 11Transplant outside: May 20 to Jun 3
Start indoors: Feb 25 to Mar 11Transplant outside: May 20 to Jun 3
Start indoors: Mar 11 to Mar 25Transplant outside: May 13 to May 27
Start indoors: Mar 11 to Mar 25Transplant outside: Apr 15 to Apr 29Sow outdoors: Apr 8 to May 13Plant for fall: Aug 6 to Sep 3
Start indoors: Mar 11 to Mar 25Transplant outside: Apr 8 to Apr 22Sow outdoors: Apr 8 to Apr 22Plant for fall: Jul 23 to Aug 13
Start indoors: Mar 11 to Mar 25Transplant outside: Apr 22 to May 6Plant for fall: Jun 25 to Jul 16
Start indoors: Mar 11 to Mar 25Transplant outside: Apr 15 to Apr 29Plant for fall: Jun 25 to Jul 16
Start indoors: Mar 11 to Mar 25Transplant outside: Apr 22 to May 6Plant for fall: Jun 25 to Jul 16
Start indoors: Mar 25 to Apr 8Transplant outside: May 27 to Jun 10Sow outdoors: May 27 to Jun 10
Start indoors: Mar 25 to Apr 8Transplant outside: May 13 to May 27
Sow outdoors: Mar 25 to Apr 15Plant for fall: Jul 9 to Jul 30
Sow outdoors: Mar 25 to Apr 15Plant for fall: Aug 6 to Aug 27
Sow outdoors: Apr 1 to May 13Plant for fall: Aug 20 to Sep 10
Start indoors: Apr 8 to Apr 15Transplant outside: May 20 to May 27Sow outdoors: May 13 to May 27Plant for fall: Jul 16 to Jul 30
Start indoors: Apr 8 to Apr 15Sow outdoors: May 13 to May 27Plant for fall: Jul 23 to Aug 6
Start indoors: Apr 8 to Apr 15Sow outdoors: May 13 to May 27
Start indoors: Apr 8 to Apr 15Transplant outside: May 20 to Jun 3
Sow outdoors: Apr 15 to May 13Plant for fall: Jul 9 to Jul 23
Sow outdoors: Apr 15 to May 13Plant for fall: Jul 23 to Aug 6
Sow outdoors: Apr 15 to May 6
Sow outdoors: Apr 22 to May 20Plant for fall: Jul 23 to Aug 6
Sow outdoors: Apr 22 to May 13Plant for fall: Aug 6 to Aug 27
Sow outdoors: May 13 to Jun 3Plant for fall: Jul 16 to Jul 30
Sow outdoors: May 13 to May 27
Transplant outside: May 20 to Jun 10
Plant for fall: Sep 17 to Oct 22
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 11 – Feb 25 | Apr 8 – Apr 22 | — | — |
| Peppers | Feb 25 – Mar 11 | May 20 – Jun 3 | — | — |
| Eggplant | Feb 25 – Mar 11 | May 20 – Jun 3 | — | — |
| Tomatoes | Mar 11 – Mar 25 | May 13 – May 27 | — | — |
| Lettuce | Mar 11 – Mar 25 | Apr 15 – Apr 29 | Apr 8 – May 13 | Aug 6 – Sep 3 |
| Kale | Mar 11 – Mar 25 | Apr 8 – Apr 22 | Apr 8 – Apr 22 | Jul 23 – Aug 13 |
| Broccoli | Mar 11 – Mar 25 | Apr 22 – May 6 | — | Jun 25 – Jul 16 |
| Cabbage | Mar 11 – Mar 25 | Apr 15 – Apr 29 | — | Jun 25 – Jul 16 |
| Cauliflower | Mar 11 – Mar 25 | Apr 22 – May 6 | — | Jun 25 – Jul 16 |
| Okra | Mar 25 – Apr 8 | May 27 – Jun 10 | May 27 – Jun 10 | — |
| Basil | Mar 25 – Apr 8 | May 13 – May 27 | — | — |
| Peas | — | — | Mar 25 – Apr 15 | Jul 9 – Jul 30 |
| Spinach | — | — | Mar 25 – Apr 15 | Aug 6 – Aug 27 |
| Radishes | — | — | Apr 1 – May 13 | Aug 20 – Sep 10 |
| Cucumbers | Apr 8 – Apr 15 | May 20 – May 27 | May 13 – May 27 | Jul 16 – Jul 30 |
| Zucchini & Summer Squash | Apr 8 – Apr 15 | — | May 13 – May 27 | Jul 23 – Aug 6 |
| Winter Squash & Pumpkins | Apr 8 – Apr 15 | — | May 13 – May 27 | — |
| Melons & Watermelon | Apr 8 – Apr 15 | May 20 – Jun 3 | — | — |
| Carrots | — | — | Apr 15 – May 13 | Jul 9 – Jul 23 |
| Beets | — | — | Apr 15 – May 13 | Jul 23 – Aug 6 |
| Potatoes | — | — | Apr 15 – May 6 | — |
| Swiss Chard | — | — | Apr 22 – May 20 | Jul 23 – Aug 6 |
| Cilantro | — | — | Apr 22 – May 13 | Aug 6 – Aug 27 |
| Green Beans | — | — | May 13 – Jun 3 | Jul 16 – Jul 30 |
| Sweet Corn | — | — | May 13 – May 27 | — |
| Sweet Potatoes | — | May 20 – Jun 10 | — | — |
| Garlic | — | — | — | Sep 17 – Oct 22 |
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 16st, MT weather station, 2 km away (elevation 3,504 ft (1,068 m)).
ZIP codes in Great Falls: 59401 59403 59404 59405 59406
Frost dates near Great Falls
- Black Eagle May 6 · Oct 1
- Malmstrom Afb May 6 · Oct 1
- Sand Coulee May 6 · Oct 1
- Floweree May 23 · Sep 23
- Vaughn Jun 2 · Sep 10
- Stockett May 6 · Oct 1
- Ulm May 21 · Sep 19
- Belt May 22 · Sep 23
Frequently asked questions
When is the last frost in Great Falls, MT?
The median last spring frost in Great Falls, MT is May 6. There is still about a 10% chance of frost after May 19, 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 October 1, with about a 10% chance of frost before September 17.
How long is the growing season in Great Falls, MT?
About 148 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.