Winston, MT frost dates
Last spring frostMay 19median date
First fall frostSep 19median date
Growing season123 daysfrost-free
Hardiness zone5aZone 5a
How Winston compares
- In 8 years out of 10, the last spring frost in Winston falls between May 8 and June 2, a 25-day window. The first fall frost falls between September 5 and October 2.
- The median last frost is the same as the Montana median of May 19.
- Its 123-day growing season is longer than 41% of the 325 Montana places with a regular frost season (state median 125 days).
- The last frost is 16 days later than the zone 5a median of May 3. Hardiness zones measure winter cold, not season length, so use these dates rather than a zone 5a chart.
- The weather station records an average of 174 nights a year at or below 32°F.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | May 8 |
| 50% (median) | May 19 |
| 10% (safe for tender plants) | June 2 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | September 5 |
| 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 Winston, MT
Winston, MT frost dates — last frost May 19, first frost Sep 19, zone 5a. 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 25 to Aug 22
Start indoors: Mar 24 to Apr 7Transplant outside: Apr 21 to May 5Sow outdoors: Apr 21 to May 5Plant for fall: Jul 11 to Aug 1
Start indoors: Mar 24 to Apr 7Transplant outside: May 5 to May 19Plant for fall: Jun 13 to Jul 4
Start indoors: Mar 24 to Apr 7Transplant outside: Apr 28 to May 12Plant for fall: Jun 13 to Jul 4
Start indoors: Mar 24 to Apr 7Transplant outside: May 5 to May 19Plant for fall: Jun 13 to Jul 4
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 27 to Jul 18
Sow outdoors: Apr 7 to Apr 28Plant for fall: Jul 25 to Aug 15
Sow outdoors: Apr 14 to May 26Plant for fall: Aug 8 to Aug 29
Start indoors: Apr 21 to Apr 28Transplant outside: Jun 2 to Jun 9Sow outdoors: May 26 to Jun 9Plant for fall: Jul 4 to Jul 18
Start indoors: Apr 21 to Apr 28Sow outdoors: May 26 to Jun 9Plant for fall: Jul 11 to Jul 25
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 27 to Jul 11
Sow outdoors: Apr 28 to May 26Plant for fall: Jul 11 to Jul 25
Sow outdoors: Apr 28 to May 19
Sow outdoors: May 5 to Jun 2Plant for fall: Jul 11 to Jul 25
Sow outdoors: May 5 to May 26Plant for fall: Jul 25 to Aug 15
Sow outdoors: May 26 to Jun 16Plant for fall: Jul 4 to Jul 18
Sow outdoors: May 26 to Jun 9
Transplant outside: Jun 2 to Jun 23
Plant for fall: Sep 5 to Oct 10
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Winston, 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 25 – Aug 22 |
| Kale | Mar 24 – Apr 7 | Apr 21 – May 5 | Apr 21 – May 5 | Jul 11 – Aug 1 |
| Broccoli | Mar 24 – Apr 7 | May 5 – May 19 | — | Jun 13 – Jul 4 |
| Cabbage | Mar 24 – Apr 7 | Apr 28 – May 12 | — | Jun 13 – Jul 4 |
| Cauliflower | Mar 24 – Apr 7 | May 5 – May 19 | — | Jun 13 – Jul 4 |
| 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 27 – Jul 18 |
| Spinach | — | — | Apr 7 – Apr 28 | Jul 25 – Aug 15 |
| Radishes | — | — | Apr 14 – May 26 | Aug 8 – Aug 29 |
| Cucumbers | Apr 21 – Apr 28 | Jun 2 – Jun 9 | May 26 – Jun 9 | Jul 4 – Jul 18 |
| Zucchini & Summer Squash | Apr 21 – Apr 28 | — | May 26 – Jun 9 | Jul 11 – Jul 25 |
| 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 27 – Jul 11 |
| Beets | — | — | Apr 28 – May 26 | Jul 11 – Jul 25 |
| Potatoes | — | — | Apr 28 – May 19 | — |
| Swiss Chard | — | — | May 5 – Jun 2 | Jul 11 – Jul 25 |
| Cilantro | — | — | May 5 – May 26 | Jul 25 – Aug 15 |
| Green Beans | — | — | May 26 – Jun 16 | Jul 4 – Jul 18 |
| Sweet Corn | — | — | May 26 – Jun 9 | — |
| Sweet Potatoes | — | Jun 2 – Jun 23 | — | — |
| 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 Townsend 3se, MT weather station, 23 km away (elevation 3,963 ft (1,208 m)).
Frost dates near Winston
- Townsend May 19 · Sep 19
- East Helena May 9 · Sep 30
- Clancy Jun 18 · Sep 5
- Radersburg May 19 · Sep 19
- Jefferson City Jun 18 · Sep 5
- Toston May 19 · Sep 19
- Helena May 9 · Sep 30
- Fort Harrison May 9 · Sep 30
- Boulder Jun 7 · Sep 8
- Basin Jun 7 · Sep 8
Frequently asked questions
When is the last frost in Winston, MT?
The median last spring frost in Winston, MT is May 19. There is still about a 10% chance of frost after June 2, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Winston, MT?
The median first fall frost is September 19, with about a 10% chance of frost before September 5.
How long is the growing season in Winston, MT?
About 123 days between the median last spring frost and first fall frost.
What planting zone is Winston, MT?
Winston, MT is in USDA hardiness zone 5a.