Grantsdale, MT frost dates
Last spring frostMay 21median date
First fall frostSep 22median date
Growing season124 daysfrost-free
Hardiness zone5bZone 5b
How Grantsdale compares
- In 8 years out of 10, the last spring frost in Grantsdale falls between May 7 and June 6, a 30-day window. The first fall frost falls between September 6 and October 5.
- The median last frost is 2 days later than the Montana median of May 19.
- Its 124-day growing season is longer than 45% of the 325 Montana places with a regular frost season (state median 125 days).
- The last frost is 20 days later than the zone 5b median of May 1. Hardiness zones measure winter cold, not season length, so use these dates rather than a zone 5b chart.
- The weather station records an average of 173 nights a year at or below 32°F.
- Compared with Missoula, MT, 76 km away, the last frost here is 11 days later than there and the growing season is 20 days shorter.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | May 7 |
| 50% (median) | May 21 |
| 10% (safe for tender plants) | June 6 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | September 6 |
| 50% (median) | September 22 |
| 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 Grantsdale, MT
Grantsdale, MT frost dates — last frost May 21, first frost Sep 22, zone 5b. whenisthelastfrost.com
Crop
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Start indoors: Feb 26 to Mar 12Transplant outside: Apr 23 to May 7
Start indoors: Mar 12 to Mar 26Transplant outside: Jun 4 to Jun 18
Start indoors: Mar 12 to Mar 26Transplant outside: Jun 4 to Jun 18
Start indoors: Mar 26 to Apr 9Transplant outside: May 28 to Jun 11
Start indoors: Mar 26 to Apr 9Transplant outside: Apr 30 to May 14Sow outdoors: Apr 23 to May 28Plant for fall: Jul 28 to Aug 25
Start indoors: Mar 26 to Apr 9Transplant outside: Apr 23 to May 7Sow outdoors: Apr 23 to May 7Plant for fall: Jul 14 to Aug 4
Start indoors: Mar 26 to Apr 9Transplant outside: May 7 to May 21Plant for fall: Jun 16 to Jul 7
Start indoors: Mar 26 to Apr 9Transplant outside: Apr 30 to May 14Plant for fall: Jun 16 to Jul 7
Start indoors: Mar 26 to Apr 9Transplant outside: May 7 to May 21Plant for fall: Jun 16 to Jul 7
Start indoors: Apr 9 to Apr 23Transplant outside: Jun 11 to Jun 25Sow outdoors: Jun 11 to Jun 25
Start indoors: Apr 9 to Apr 23Transplant outside: May 28 to Jun 11
Sow outdoors: Apr 9 to Apr 30Plant for fall: Jun 30 to Jul 21
Sow outdoors: Apr 9 to Apr 30Plant for fall: Jul 28 to Aug 18
Sow outdoors: Apr 16 to May 28Plant for fall: Aug 11 to Sep 1
Start indoors: Apr 23 to Apr 30Transplant outside: Jun 4 to Jun 11Sow outdoors: May 28 to Jun 11Plant for fall: Jul 7 to Jul 21
Start indoors: Apr 23 to Apr 30Sow outdoors: May 28 to Jun 11Plant for fall: Jul 14 to Jul 28
Start indoors: Apr 23 to Apr 30Sow outdoors: May 28 to Jun 11
Start indoors: Apr 23 to Apr 30Transplant outside: Jun 4 to Jun 18
Sow outdoors: Apr 30 to May 28Plant for fall: Jun 30 to Jul 14
Sow outdoors: Apr 30 to May 28Plant for fall: Jul 14 to Jul 28
Sow outdoors: Apr 30 to May 21
Sow outdoors: May 7 to Jun 4Plant for fall: Jul 14 to Jul 28
Sow outdoors: May 7 to May 28Plant for fall: Jul 28 to Aug 18
Sow outdoors: May 28 to Jun 18Plant for fall: Jul 7 to Jul 21
Sow outdoors: May 28 to Jun 11
Transplant outside: Jun 4 to Jun 25
Plant for fall: Sep 8 to Oct 13
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Grantsdale, MT
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Feb 26 – Mar 12 | Apr 23 – May 7 | — | — |
| Peppers | Mar 12 – Mar 26 | Jun 4 – Jun 18 | — | — |
| Eggplant | Mar 12 – Mar 26 | Jun 4 – Jun 18 | — | — |
| Tomatoes | Mar 26 – Apr 9 | May 28 – Jun 11 | — | — |
| Lettuce | Mar 26 – Apr 9 | Apr 30 – May 14 | Apr 23 – May 28 | Jul 28 – Aug 25 |
| Kale | Mar 26 – Apr 9 | Apr 23 – May 7 | Apr 23 – May 7 | Jul 14 – Aug 4 |
| Broccoli | Mar 26 – Apr 9 | May 7 – May 21 | — | Jun 16 – Jul 7 |
| Cabbage | Mar 26 – Apr 9 | Apr 30 – May 14 | — | Jun 16 – Jul 7 |
| Cauliflower | Mar 26 – Apr 9 | May 7 – May 21 | — | Jun 16 – Jul 7 |
| Okra | Apr 9 – Apr 23 | Jun 11 – Jun 25 | Jun 11 – Jun 25 | — |
| Basil | Apr 9 – Apr 23 | May 28 – Jun 11 | — | — |
| Peas | — | — | Apr 9 – Apr 30 | Jun 30 – Jul 21 |
| Spinach | — | — | Apr 9 – Apr 30 | Jul 28 – Aug 18 |
| Radishes | — | — | Apr 16 – May 28 | Aug 11 – Sep 1 |
| Cucumbers | Apr 23 – Apr 30 | Jun 4 – Jun 11 | May 28 – Jun 11 | Jul 7 – Jul 21 |
| Zucchini & Summer Squash | Apr 23 – Apr 30 | — | May 28 – Jun 11 | Jul 14 – Jul 28 |
| Winter Squash & Pumpkins | Apr 23 – Apr 30 | — | May 28 – Jun 11 | — |
| Melons & Watermelon | Apr 23 – Apr 30 | Jun 4 – Jun 18 | — | — |
| Carrots | — | — | Apr 30 – May 28 | Jun 30 – Jul 14 |
| Beets | — | — | Apr 30 – May 28 | Jul 14 – Jul 28 |
| Potatoes | — | — | Apr 30 – May 21 | — |
| Swiss Chard | — | — | May 7 – Jun 4 | Jul 14 – Jul 28 |
| Cilantro | — | — | May 7 – May 28 | Jul 28 – Aug 18 |
| Green Beans | — | — | May 28 – Jun 18 | Jul 7 – Jul 21 |
| Sweet Corn | — | — | May 28 – Jun 11 | — |
| Sweet Potatoes | — | Jun 4 – Jun 25 | — | — |
| Garlic | — | — | — | Sep 8 – Oct 13 |
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 Hamilton, MT weather station, 5 km away (elevation 3,586 ft (1,093 m)).
Frost dates near Grantsdale
- Hamilton May 21 · Sep 22
- Corvallis May 23 · Sep 21
- Pinesdale May 21 · Sep 22
- Darby May 24 · Sep 23
- Victor May 23 · Sep 21
- Conner frost any month
- Stevensville May 22 · Sep 19
- Sula frost any month
- Florence May 22 · Sep 19
- Lolo May 16 · Sep 26
Frequently asked questions
When is the last frost in Grantsdale, MT?
The median last spring frost in Grantsdale, MT is May 21. There is still about a 10% chance of frost after June 6, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Grantsdale, MT?
The median first fall frost is September 22, with about a 10% chance of frost before September 6.
How long is the growing season in Grantsdale, MT?
About 124 days between the median last spring frost and first fall frost.
What planting zone is Grantsdale, MT?
Grantsdale, MT is in USDA hardiness zone 5b.