Brockton, MT frost dates
Last spring frostMay 24median date
First fall frostSep 14median date
Growing season113 daysfrost-free
Hardiness zone4aZone 4a
How Brockton compares
- In 8 years out of 10, the last spring frost in Brockton falls between May 12 and June 6, a 25-day window. The first fall frost falls between September 1 and September 25.
- The median last frost is 5 days later than the Montana median of May 19.
- Its 113-day growing season is longer than 25% of the 325 Montana places with a regular frost season (state median 125 days).
- The last frost is 12 days later than the zone 4a median of May 12. Hardiness zones measure winter cold, not season length, so use these dates rather than a zone 4a chart.
- The weather station records an average of 206 nights a year at or below 32°F.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | May 12 |
| 50% (median) | May 24 |
| 10% (safe for tender plants) | June 6 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | September 1 |
| 50% (median) | September 14 |
| 90% (late) | September 25 |
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 Brockton, MT
Brockton, MT frost dates — last frost May 24, first frost Sep 14, zone 4a. whenisthelastfrost.com
Crop
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Start indoors: Mar 1 to Mar 15Transplant outside: Apr 26 to May 10
Start indoors: Mar 15 to Mar 29Transplant outside: Jun 7 to Jun 21
Start indoors: Mar 15 to Mar 29Transplant outside: Jun 7 to Jun 21
Start indoors: Mar 29 to Apr 12Transplant outside: May 31 to Jun 14
Start indoors: Mar 29 to Apr 12Transplant outside: May 3 to May 17Sow outdoors: Apr 26 to May 31Plant for fall: Jul 20 to Aug 17
Start indoors: Mar 29 to Apr 12Transplant outside: Apr 26 to May 10Sow outdoors: Apr 26 to May 10Plant for fall: Jul 6 to Jul 27
Start indoors: Mar 29 to Apr 12Transplant outside: May 10 to May 24Plant for fall: Jun 8 to Jun 29
Start indoors: Mar 29 to Apr 12Transplant outside: May 3 to May 17Plant for fall: Jun 8 to Jun 29
Start indoors: Mar 29 to Apr 12Transplant outside: May 10 to May 24Plant for fall: Jun 8 to Jun 29
Start indoors: Apr 12 to Apr 26Transplant outside: Jun 14 to Jun 28Sow outdoors: Jun 14 to Jun 28
Start indoors: Apr 12 to Apr 26Transplant outside: May 31 to Jun 14
Sow outdoors: Apr 12 to May 3Plant for fall: Jun 22 to Jul 13
Sow outdoors: Apr 12 to May 3Plant for fall: Jul 20 to Aug 10
Sow outdoors: Apr 19 to May 31Plant for fall: Aug 3 to Aug 24
Start indoors: Apr 26 to May 3Transplant outside: Jun 7 to Jun 14Sow outdoors: May 31 to Jun 14Plant for fall: Jun 29 to Jul 13
Start indoors: Apr 26 to May 3Sow outdoors: May 31 to Jun 14Plant for fall: Jul 6 to Jul 20
Start indoors: Apr 26 to May 3Sow outdoors: May 31 to Jun 14
Start indoors: Apr 26 to May 3Transplant outside: Jun 7 to Jun 21
Sow outdoors: May 3 to May 31Plant for fall: Jun 22 to Jul 6
Sow outdoors: May 3 to May 31Plant for fall: Jul 6 to Jul 20
Sow outdoors: May 3 to May 24
Sow outdoors: May 10 to Jun 7Plant for fall: Jul 6 to Jul 20
Sow outdoors: May 10 to May 31Plant for fall: Jul 20 to Aug 10
Sow outdoors: May 31 to Jun 21
Sow outdoors: May 31 to Jun 14
Transplant outside: Jun 7 to Jun 28
Plant for fall: Aug 31 to Oct 5
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Brockton, MT
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Mar 1 – Mar 15 | Apr 26 – May 10 | — | — |
| Peppers | Mar 15 – Mar 29 | Jun 7 – Jun 21 | — | — |
| Eggplant | Mar 15 – Mar 29 | Jun 7 – Jun 21 | — | — |
| Tomatoes | Mar 29 – Apr 12 | May 31 – Jun 14 | — | — |
| Lettuce | Mar 29 – Apr 12 | May 3 – May 17 | Apr 26 – May 31 | Jul 20 – Aug 17 |
| Kale | Mar 29 – Apr 12 | Apr 26 – May 10 | Apr 26 – May 10 | Jul 6 – Jul 27 |
| Broccoli | Mar 29 – Apr 12 | May 10 – May 24 | — | Jun 8 – Jun 29 |
| Cabbage | Mar 29 – Apr 12 | May 3 – May 17 | — | Jun 8 – Jun 29 |
| Cauliflower | Mar 29 – Apr 12 | May 10 – May 24 | — | Jun 8 – Jun 29 |
| Okra | Apr 12 – Apr 26 | Jun 14 – Jun 28 | Jun 14 – Jun 28 | — |
| Basil | Apr 12 – Apr 26 | May 31 – Jun 14 | — | — |
| Peas | — | — | Apr 12 – May 3 | Jun 22 – Jul 13 |
| Spinach | — | — | Apr 12 – May 3 | Jul 20 – Aug 10 |
| Radishes | — | — | Apr 19 – May 31 | Aug 3 – Aug 24 |
| Cucumbers | Apr 26 – May 3 | Jun 7 – Jun 14 | May 31 – Jun 14 | Jun 29 – Jul 13 |
| Zucchini & Summer Squash | Apr 26 – May 3 | — | May 31 – Jun 14 | Jul 6 – Jul 20 |
| Winter Squash & Pumpkins Warning: Your frost-free season is about 113 days, which is tight for winter squash & pumpkins (100+ days). Choose early varieties and use transplants or row covers. | Apr 26 – May 3 | — | May 31 – Jun 14 | — |
| Melons & Watermelon | Apr 26 – May 3 | Jun 7 – Jun 21 | — | — |
| Carrots | — | — | May 3 – May 31 | Jun 22 – Jul 6 |
| Beets | — | — | May 3 – May 31 | Jul 6 – Jul 20 |
| Potatoes | — | — | May 3 – May 24 | — |
| Swiss Chard | — | — | May 10 – Jun 7 | Jul 6 – Jul 20 |
| Cilantro | — | — | May 10 – May 31 | Jul 20 – Aug 10 |
| Green Beans | — | — | May 31 – Jun 21 | — |
| Sweet Corn | — | — | May 31 – Jun 14 | — |
| Sweet Potatoes Warning: Your frost-free season is about 113 days, which is tight for sweet potatoes (100+ days). Choose early varieties and use transplants or row covers. | — | Jun 7 – Jun 28 | — | — |
| Garlic | — | — | — | Aug 31 – Oct 5 |
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 Wolf Point 29 Ene, MT weather station, 21 km away (elevation 2,087 ft (636 m)).
Frost dates near Brockton
- Poplar May 24 · Sep 14
- Culbertson May 21 · Sep 20
- Froid May 16 · Sep 18
- Homestead May 16 · Sep 18
- Medicine Lake May 16 · Sep 18
- Reserve May 16 · Sep 18
- Bainville May 21 · Sep 20
- Lambert May 11 · Sep 27
- Redstone May 28 · Sep 7
- Fairview May 11 · Sep 27
Frequently asked questions
When is the last frost in Brockton, MT?
The median last spring frost in Brockton, MT is May 24. 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 Brockton, MT?
The median first fall frost is September 14, with about a 10% chance of frost before September 1.
How long is the growing season in Brockton, MT?
About 113 days between the median last spring frost and first fall frost.
What planting zone is Brockton, MT?
Brockton, MT is in USDA hardiness zone 4a.