Augusta, MT frost dates
Last spring frostMay 19median date
First fall frostSep 21median date
Growing season125 daysfrost-free
Hardiness zone4bZone 4b
How Augusta compares
- In 8 years out of 10, the last spring frost in Augusta falls between May 4 and May 31, a 27-day window. The first fall frost falls between September 4 and October 4.
- The median last frost is the same as 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 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 177 nights a year at or below 32°F.
- Compared with Great Falls, MT, 84 km away, the last frost here is 13 days later than there and the growing season is 23 days shorter.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | May 4 |
| 50% (median) | May 19 |
| 10% (safe for tender plants) | May 31 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | September 4 |
| 50% (median) | September 21 |
| 90% (late) | October 4 |
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 Augusta, MT
Augusta, MT frost dates — last frost May 19, first frost Sep 21, 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 27 to Aug 24
Start indoors: Mar 24 to Apr 7Transplant outside: Apr 21 to May 5Sow outdoors: Apr 21 to May 5Plant for fall: Jul 13 to Aug 3
Start indoors: Mar 24 to Apr 7Transplant outside: May 5 to May 19Plant for fall: Jun 15 to Jul 6
Start indoors: Mar 24 to Apr 7Transplant outside: Apr 28 to May 12Plant for fall: Jun 15 to Jul 6
Start indoors: Mar 24 to Apr 7Transplant outside: May 5 to May 19Plant for fall: Jun 15 to Jul 6
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: Jun 29 to Jul 20
Sow outdoors: Apr 7 to Apr 28Plant for fall: Jul 27 to Aug 17
Sow outdoors: Apr 14 to May 26Plant for fall: Aug 10 to Aug 31
Start indoors: Apr 21 to Apr 28Transplant outside: Jun 2 to Jun 9Sow outdoors: May 26 to Jun 9Plant for fall: Jul 6 to Jul 20
Start indoors: Apr 21 to Apr 28Sow outdoors: May 26 to Jun 9Plant for fall: Jul 13 to Jul 27
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: Jun 29 to Jul 13
Sow outdoors: Apr 28 to May 26Plant for fall: Jul 13 to Jul 27
Sow outdoors: Apr 28 to May 19
Sow outdoors: May 5 to Jun 2Plant for fall: Jul 13 to Jul 27
Sow outdoors: May 5 to May 26Plant for fall: Jul 27 to Aug 17
Sow outdoors: May 26 to Jun 16Plant for fall: Jul 6 to Jul 20
Sow outdoors: May 26 to Jun 9
Transplant outside: Jun 2 to Jun 23
Plant for fall: Sep 7 to Oct 12
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Augusta, 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 27 – Aug 24 |
| Kale | Mar 24 – Apr 7 | Apr 21 – May 5 | Apr 21 – May 5 | Jul 13 – Aug 3 |
| Broccoli | Mar 24 – Apr 7 | May 5 – May 19 | — | Jun 15 – Jul 6 |
| Cabbage | Mar 24 – Apr 7 | Apr 28 – May 12 | — | Jun 15 – Jul 6 |
| Cauliflower | Mar 24 – Apr 7 | May 5 – May 19 | — | Jun 15 – Jul 6 |
| 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 | Jun 29 – Jul 20 |
| Spinach | — | — | Apr 7 – Apr 28 | Jul 27 – Aug 17 |
| Radishes | — | — | Apr 14 – May 26 | Aug 10 – Aug 31 |
| Cucumbers | Apr 21 – Apr 28 | Jun 2 – Jun 9 | May 26 – Jun 9 | Jul 6 – Jul 20 |
| Zucchini & Summer Squash | Apr 21 – Apr 28 | — | May 26 – Jun 9 | Jul 13 – Jul 27 |
| 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 | Jun 29 – Jul 13 |
| Beets | — | — | Apr 28 – May 26 | Jul 13 – Jul 27 |
| Potatoes | — | — | Apr 28 – May 19 | — |
| Swiss Chard | — | — | May 5 – Jun 2 | Jul 13 – Jul 27 |
| Cilantro | — | — | May 5 – May 26 | Jul 27 – Aug 17 |
| Green Beans | — | — | May 26 – Jun 16 | Jul 6 – Jul 20 |
| Sweet Corn | — | — | May 26 – Jun 9 | — |
| Sweet Potatoes | — | Jun 2 – Jun 23 | — | — |
| Garlic | — | — | — | Sep 7 – Oct 12 |
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 Augusta, MT weather station, 4 km away (elevation 4,072 ft (1,241 m)).
Frost dates near Augusta
- Fairfield May 13 · Sep 27
- Simms Jun 2 · Sep 10
- Fort Shaw Jun 2 · Sep 10
- Wolf Creek May 19 · Sep 24
- Choteau May 28 · Sep 12
- Sun River Jun 2 · Sep 10
- Cascade May 21 · Sep 19
- Power May 13 · Sep 27
- Lincoln frost any month
- Bynum May 16 · Sep 27
Frequently asked questions
When is the last frost in Augusta, MT?
The median last spring frost in Augusta, MT is May 19. There is still about a 10% chance of frost after May 31, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Augusta, MT?
The median first fall frost is September 21, with about a 10% chance of frost before September 4.
How long is the growing season in Augusta, MT?
About 125 days between the median last spring frost and first fall frost.
What planting zone is Augusta, MT?
Augusta, MT is in USDA hardiness zone 4b.