Sunburst, MT frost dates
Last spring frostMay 17median date
First fall frostSep 25median date
Growing season131 daysfrost-free
Hardiness zone4aZone 4a
How Sunburst compares
- In 8 years out of 10, the last spring frost in Sunburst falls between May 2 and May 31, a 29-day window. The first fall frost falls between September 9 and October 6.
- The median last frost is 2 days earlier than the Montana median of May 19.
- Its 131-day growing season is longer than 62% of the 325 Montana places with a regular frost season (state median 125 days).
- The last frost is 5 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 181 nights a year at or below 32°F.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | May 2 |
| 50% (median) | May 17 |
| 10% (safe for tender plants) | May 31 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | September 9 |
| 50% (median) | September 25 |
| 90% (late) | October 6 |
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 Sunburst, MT
Sunburst, MT frost dates — last frost May 17, first frost Sep 25, zone 4a. whenisthelastfrost.com
Crop
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Start indoors: Feb 22 to Mar 8Transplant outside: Apr 19 to May 3
Start indoors: Mar 8 to Mar 22Transplant outside: May 31 to Jun 14
Start indoors: Mar 8 to Mar 22Transplant outside: May 31 to Jun 14
Start indoors: Mar 22 to Apr 5Transplant outside: May 24 to Jun 7
Start indoors: Mar 22 to Apr 5Transplant outside: Apr 26 to May 10Sow outdoors: Apr 19 to May 24Plant for fall: Jul 31 to Aug 28
Start indoors: Mar 22 to Apr 5Transplant outside: Apr 19 to May 3Sow outdoors: Apr 19 to May 3Plant for fall: Jul 17 to Aug 7
Start indoors: Mar 22 to Apr 5Transplant outside: May 3 to May 17Plant for fall: Jun 19 to Jul 10
Start indoors: Mar 22 to Apr 5Transplant outside: Apr 26 to May 10Plant for fall: Jun 19 to Jul 10
Start indoors: Mar 22 to Apr 5Transplant outside: May 3 to May 17Plant for fall: Jun 19 to Jul 10
Start indoors: Apr 5 to Apr 19Transplant outside: Jun 7 to Jun 21Sow outdoors: Jun 7 to Jun 21
Start indoors: Apr 5 to Apr 19Transplant outside: May 24 to Jun 7
Sow outdoors: Apr 5 to Apr 26Plant for fall: Jul 3 to Jul 24
Sow outdoors: Apr 5 to Apr 26Plant for fall: Jul 31 to Aug 21
Sow outdoors: Apr 12 to May 24Plant for fall: Aug 14 to Sep 4
Start indoors: Apr 19 to Apr 26Transplant outside: May 31 to Jun 7Sow outdoors: May 24 to Jun 7Plant for fall: Jul 10 to Jul 24
Start indoors: Apr 19 to Apr 26Sow outdoors: May 24 to Jun 7Plant for fall: Jul 17 to Jul 31
Start indoors: Apr 19 to Apr 26Sow outdoors: May 24 to Jun 7
Start indoors: Apr 19 to Apr 26Transplant outside: May 31 to Jun 14
Sow outdoors: Apr 26 to May 24Plant for fall: Jul 3 to Jul 17
Sow outdoors: Apr 26 to May 24Plant for fall: Jul 17 to Jul 31
Sow outdoors: Apr 26 to May 17
Sow outdoors: May 3 to May 31Plant for fall: Jul 17 to Jul 31
Sow outdoors: May 3 to May 24Plant for fall: Jul 31 to Aug 21
Sow outdoors: May 24 to Jun 14Plant for fall: Jul 10 to Jul 24
Sow outdoors: May 24 to Jun 7
Transplant outside: May 31 to Jun 21
Plant for fall: Sep 11 to Oct 16
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Sunburst, MT
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Feb 22 – Mar 8 | Apr 19 – May 3 | — | — |
| Peppers | Mar 8 – Mar 22 | May 31 – Jun 14 | — | — |
| Eggplant | Mar 8 – Mar 22 | May 31 – Jun 14 | — | — |
| Tomatoes | Mar 22 – Apr 5 | May 24 – Jun 7 | — | — |
| Lettuce | Mar 22 – Apr 5 | Apr 26 – May 10 | Apr 19 – May 24 | Jul 31 – Aug 28 |
| Kale | Mar 22 – Apr 5 | Apr 19 – May 3 | Apr 19 – May 3 | Jul 17 – Aug 7 |
| Broccoli | Mar 22 – Apr 5 | May 3 – May 17 | — | Jun 19 – Jul 10 |
| Cabbage | Mar 22 – Apr 5 | Apr 26 – May 10 | — | Jun 19 – Jul 10 |
| Cauliflower | Mar 22 – Apr 5 | May 3 – May 17 | — | Jun 19 – Jul 10 |
| Okra | Apr 5 – Apr 19 | Jun 7 – Jun 21 | Jun 7 – Jun 21 | — |
| Basil | Apr 5 – Apr 19 | May 24 – Jun 7 | — | — |
| Peas | — | — | Apr 5 – Apr 26 | Jul 3 – Jul 24 |
| Spinach | — | — | Apr 5 – Apr 26 | Jul 31 – Aug 21 |
| Radishes | — | — | Apr 12 – May 24 | Aug 14 – Sep 4 |
| Cucumbers | Apr 19 – Apr 26 | May 31 – Jun 7 | May 24 – Jun 7 | Jul 10 – Jul 24 |
| Zucchini & Summer Squash | Apr 19 – Apr 26 | — | May 24 – Jun 7 | Jul 17 – Jul 31 |
| Winter Squash & Pumpkins | Apr 19 – Apr 26 | — | May 24 – Jun 7 | — |
| Melons & Watermelon | Apr 19 – Apr 26 | May 31 – Jun 14 | — | — |
| Carrots | — | — | Apr 26 – May 24 | Jul 3 – Jul 17 |
| Beets | — | — | Apr 26 – May 24 | Jul 17 – Jul 31 |
| Potatoes | — | — | Apr 26 – May 17 | — |
| Swiss Chard | — | — | May 3 – May 31 | Jul 17 – Jul 31 |
| Cilantro | — | — | May 3 – May 24 | Jul 31 – Aug 21 |
| Green Beans | — | — | May 24 – Jun 14 | Jul 10 – Jul 24 |
| Sweet Corn | — | — | May 24 – Jun 7 | — |
| Sweet Potatoes | — | May 31 – Jun 21 | — | — |
| 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 Sunburst 8 E, MT weather station, 4 km away (elevation 3,701 ft (1,128 m)).
Frost dates near Sunburst
- Oilmont May 17 · Sep 25
- Kevin May 17 · Sep 25
- Galata May 23 · Sep 14
- Sweet Grass May 15 · Sep 25
- Shelby May 23 · Sep 16
- Ethridge May 24 · Sep 15
- Whitlash frost any month
- Cut Bank May 24 · Sep 15
- Lothair May 24 · Sep 17
- Ledger May 16 · Sep 23
Frequently asked questions
When is the last frost in Sunburst, MT?
The median last spring frost in Sunburst, MT is May 17. There is still about a 10% chance of frost after May 31, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Sunburst, MT?
The median first fall frost is September 25, with about a 10% chance of frost before September 9.
How long is the growing season in Sunburst, MT?
About 131 days between the median last spring frost and first fall frost.
What planting zone is Sunburst, MT?
Sunburst, MT is in USDA hardiness zone 4a.