Forest Grove, MT frost dates
Last spring frostMay 19median date
First fall frostSep 25median date
Growing season129 daysfrost-free
Hardiness zone4bZone 4b
How Forest Grove compares
- In 8 years out of 10, the last spring frost in Forest Grove falls between May 7 and June 1, a 25-day window. The first fall frost falls between September 11 and October 9.
- The median last frost is the same as the Montana median of May 19.
- Its 129-day growing season is longer than 57% 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 172 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 1 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | September 11 |
| 50% (median) | September 25 |
| 90% (late) | October 9 |
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 Forest Grove, MT
Forest Grove, MT frost dates — last frost May 19, first frost Sep 25, 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 31 to Aug 28
Start indoors: Mar 24 to Apr 7Transplant outside: Apr 21 to May 5Sow outdoors: Apr 21 to May 5Plant for fall: Jul 17 to Aug 7
Start indoors: Mar 24 to Apr 7Transplant outside: May 5 to May 19Plant for fall: Jun 19 to Jul 10
Start indoors: Mar 24 to Apr 7Transplant outside: Apr 28 to May 12Plant for fall: Jun 19 to Jul 10
Start indoors: Mar 24 to Apr 7Transplant outside: May 5 to May 19Plant for fall: Jun 19 to Jul 10
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 3 to Jul 24
Sow outdoors: Apr 7 to Apr 28Plant for fall: Jul 31 to Aug 21
Sow outdoors: Apr 14 to May 26Plant for fall: Aug 14 to Sep 4
Start indoors: Apr 21 to Apr 28Transplant outside: Jun 2 to Jun 9Sow outdoors: May 26 to Jun 9Plant for fall: Jul 10 to Jul 24
Start indoors: Apr 21 to Apr 28Sow outdoors: May 26 to Jun 9Plant for fall: Jul 17 to Jul 31
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 3 to Jul 17
Sow outdoors: Apr 28 to May 26Plant for fall: Jul 17 to Jul 31
Sow outdoors: Apr 28 to May 19
Sow outdoors: May 5 to Jun 2Plant for fall: Jul 17 to Jul 31
Sow outdoors: May 5 to May 26Plant for fall: Jul 31 to Aug 21
Sow outdoors: May 26 to Jun 16Plant for fall: Jul 10 to Jul 24
Sow outdoors: May 26 to Jun 9
Transplant outside: Jun 2 to Jun 23
Plant for fall: Sep 11 to Oct 16
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Forest Grove, 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 31 – Aug 28 |
| Kale | Mar 24 – Apr 7 | Apr 21 – May 5 | Apr 21 – May 5 | Jul 17 – Aug 7 |
| Broccoli | Mar 24 – Apr 7 | May 5 – May 19 | — | Jun 19 – Jul 10 |
| Cabbage | Mar 24 – Apr 7 | Apr 28 – May 12 | — | Jun 19 – Jul 10 |
| Cauliflower | Mar 24 – Apr 7 | May 5 – May 19 | — | Jun 19 – Jul 10 |
| 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 3 – Jul 24 |
| Spinach | — | — | Apr 7 – Apr 28 | Jul 31 – Aug 21 |
| Radishes | — | — | Apr 14 – May 26 | Aug 14 – Sep 4 |
| Cucumbers | Apr 21 – Apr 28 | Jun 2 – Jun 9 | May 26 – Jun 9 | Jul 10 – Jul 24 |
| Zucchini & Summer Squash | Apr 21 – Apr 28 | — | May 26 – Jun 9 | Jul 17 – Jul 31 |
| 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 3 – Jul 17 |
| Beets | — | — | Apr 28 – May 26 | Jul 17 – Jul 31 |
| Potatoes | — | — | Apr 28 – May 19 | — |
| Swiss Chard | — | — | May 5 – Jun 2 | Jul 17 – Jul 31 |
| Cilantro | — | — | May 5 – May 26 | Jul 31 – Aug 21 |
| Green Beans | — | — | May 26 – Jun 16 | Jul 10 – Jul 24 |
| Sweet Corn | — | — | May 26 – Jun 9 | — |
| Sweet Potatoes | — | Jun 2 – Jun 23 | — | — |
| Garlic | — | — | — | Sep 11 – Oct 16 |
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 Lewistown 11ese, MT weather station, 11 km away (elevation 5,030 ft (1,533 m)).
Frost dates near Forest Grove
- Grass Range May 20 · Sep 24
- Lewistown May 14 · Sep 28
- Hilger May 14 · Sep 28
- Teigen May 20 · Sep 24
- Roy May 14 · Sep 24
- Moore May 23 · Sep 21
- Winnett May 16 · Sep 28
- Judith Gap Jun 1 · Sep 15
- Buffalo Jun 1 · Sep 15
- Hobson May 28 · Sep 20
Frequently asked questions
When is the last frost in Forest Grove, MT?
The median last spring frost in Forest Grove, MT is May 19. There is still about a 10% chance of frost after June 1, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Forest Grove, MT?
The median first fall frost is September 25, with about a 10% chance of frost before September 11.
How long is the growing season in Forest Grove, MT?
About 129 days between the median last spring frost and first fall frost.
What planting zone is Forest Grove, MT?
Forest Grove, MT is in USDA hardiness zone 4b.