Brockway, MT frost dates
Last spring frostMay 20median date
First fall frostSep 19median date
Growing season122 daysfrost-free
Hardiness zone4aZone 4a
How Brockway compares
- In 8 years out of 10, the last spring frost in Brockway falls between May 6 and June 5, a 30-day window. The first fall frost falls between September 4 and October 2.
- The median last frost is 1 day later than the Montana median of May 19.
- Its 122-day growing season is longer than 38% of the 325 Montana places with a regular frost season (state median 125 days).
- The last frost is 8 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 183 nights a year at or below 32°F.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | May 6 |
| 50% (median) | May 20 |
| 10% (safe for tender plants) | June 5 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | September 4 |
| 50% (median) | September 19 |
| 90% (late) | October 2 |
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 Brockway, MT
Brockway, MT frost dates — last frost May 20, first frost Sep 19, zone 4a. whenisthelastfrost.com
Crop
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Start indoors: Feb 25 to Mar 11Transplant outside: Apr 22 to May 6
Start indoors: Mar 11 to Mar 25Transplant outside: Jun 3 to Jun 17
Start indoors: Mar 11 to Mar 25Transplant outside: Jun 3 to Jun 17
Start indoors: Mar 25 to Apr 8Transplant outside: May 27 to Jun 10
Start indoors: Mar 25 to Apr 8Transplant outside: Apr 29 to May 13Sow outdoors: Apr 22 to May 27Plant for fall: Jul 25 to Aug 22
Start indoors: Mar 25 to Apr 8Transplant outside: Apr 22 to May 6Sow outdoors: Apr 22 to May 6Plant for fall: Jul 11 to Aug 1
Start indoors: Mar 25 to Apr 8Transplant outside: May 6 to May 20Plant for fall: Jun 13 to Jul 4
Start indoors: Mar 25 to Apr 8Transplant outside: Apr 29 to May 13Plant for fall: Jun 13 to Jul 4
Start indoors: Mar 25 to Apr 8Transplant outside: May 6 to May 20Plant for fall: Jun 13 to Jul 4
Start indoors: Apr 8 to Apr 22Transplant outside: Jun 10 to Jun 24Sow outdoors: Jun 10 to Jun 24
Start indoors: Apr 8 to Apr 22Transplant outside: May 27 to Jun 10
Sow outdoors: Apr 8 to Apr 29Plant for fall: Jun 27 to Jul 18
Sow outdoors: Apr 8 to Apr 29Plant for fall: Jul 25 to Aug 15
Sow outdoors: Apr 15 to May 27Plant for fall: Aug 8 to Aug 29
Start indoors: Apr 22 to Apr 29Transplant outside: Jun 3 to Jun 10Sow outdoors: May 27 to Jun 10Plant for fall: Jul 4 to Jul 18
Start indoors: Apr 22 to Apr 29Sow outdoors: May 27 to Jun 10Plant for fall: Jul 11 to Jul 25
Start indoors: Apr 22 to Apr 29Sow outdoors: May 27 to Jun 10
Start indoors: Apr 22 to Apr 29Transplant outside: Jun 3 to Jun 17
Sow outdoors: Apr 29 to May 27Plant for fall: Jun 27 to Jul 11
Sow outdoors: Apr 29 to May 27Plant for fall: Jul 11 to Jul 25
Sow outdoors: Apr 29 to May 20
Sow outdoors: May 6 to Jun 3Plant for fall: Jul 11 to Jul 25
Sow outdoors: May 6 to May 27Plant for fall: Jul 25 to Aug 15
Sow outdoors: May 27 to Jun 17Plant for fall: Jul 4 to Jul 18
Sow outdoors: May 27 to Jun 10
Transplant outside: Jun 3 to Jun 24
Plant for fall: Sep 5 to Oct 10
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Brockway, MT
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Feb 25 – Mar 11 | Apr 22 – May 6 | — | — |
| Peppers | Mar 11 – Mar 25 | Jun 3 – Jun 17 | — | — |
| Eggplant | Mar 11 – Mar 25 | Jun 3 – Jun 17 | — | — |
| Tomatoes | Mar 25 – Apr 8 | May 27 – Jun 10 | — | — |
| Lettuce | Mar 25 – Apr 8 | Apr 29 – May 13 | Apr 22 – May 27 | Jul 25 – Aug 22 |
| Kale | Mar 25 – Apr 8 | Apr 22 – May 6 | Apr 22 – May 6 | Jul 11 – Aug 1 |
| Broccoli | Mar 25 – Apr 8 | May 6 – May 20 | — | Jun 13 – Jul 4 |
| Cabbage | Mar 25 – Apr 8 | Apr 29 – May 13 | — | Jun 13 – Jul 4 |
| Cauliflower | Mar 25 – Apr 8 | May 6 – May 20 | — | Jun 13 – Jul 4 |
| Okra | Apr 8 – Apr 22 | Jun 10 – Jun 24 | Jun 10 – Jun 24 | — |
| Basil | Apr 8 – Apr 22 | May 27 – Jun 10 | — | — |
| Peas | — | — | Apr 8 – Apr 29 | Jun 27 – Jul 18 |
| Spinach | — | — | Apr 8 – Apr 29 | Jul 25 – Aug 15 |
| Radishes | — | — | Apr 15 – May 27 | Aug 8 – Aug 29 |
| Cucumbers | Apr 22 – Apr 29 | Jun 3 – Jun 10 | May 27 – Jun 10 | Jul 4 – Jul 18 |
| Zucchini & Summer Squash | Apr 22 – Apr 29 | — | May 27 – Jun 10 | Jul 11 – Jul 25 |
| Winter Squash & Pumpkins | Apr 22 – Apr 29 | — | May 27 – Jun 10 | — |
| Melons & Watermelon | Apr 22 – Apr 29 | Jun 3 – Jun 17 | — | — |
| Carrots | — | — | Apr 29 – May 27 | Jun 27 – Jul 11 |
| Beets | — | — | Apr 29 – May 27 | Jul 11 – Jul 25 |
| Potatoes | — | — | Apr 29 – May 20 | — |
| Swiss Chard | — | — | May 6 – Jun 3 | Jul 11 – Jul 25 |
| Cilantro | — | — | May 6 – May 27 | Jul 25 – Aug 15 |
| Green Beans | — | — | May 27 – Jun 17 | Jul 4 – Jul 18 |
| Sweet Corn | — | — | May 27 – Jun 10 | — |
| Sweet Potatoes | — | Jun 3 – Jun 24 | — | — |
| Garlic | — | — | — | Sep 5 – Oct 10 |
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 Brockway 3 Wsw, MT weather station, 6 km away (elevation 2,631 ft (802 m)).
Frost dates near Brockway
- Circle May 17 · Sep 22
- Lindsay May 26 · Sep 17
- Terry May 12 · Sep 28
- Cohagen May 25 · Sep 14
- Bloomfield May 3 · Oct 4
- Angela May 15 · Sep 25
- Vida May 16 · Sep 22
- Richey May 16 · Sep 22
- Fallon May 20 · Sep 22
- Kinsey May 8 · Sep 30
Frequently asked questions
When is the last frost in Brockway, MT?
The median last spring frost in Brockway, MT is May 20. There is still about a 10% chance of frost after June 5, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Brockway, MT?
The median first fall frost is September 19, with about a 10% chance of frost before September 4.
How long is the growing season in Brockway, MT?
About 122 days between the median last spring frost and first fall frost.
What planting zone is Brockway, MT?
Brockway, MT is in USDA hardiness zone 4a.