Chester, MT frost dates
Last spring frostMay 24median date
First fall frostSep 17median date
Growing season116 daysfrost-free
Hardiness zone4aZone 4a
How Chester compares
- In 8 years out of 10, the last spring frost in Chester falls between May 11 and June 9, a 29-day window. The first fall frost falls between September 3 and September 29.
- The median last frost is 5 days later than the Montana median of May 19.
- Its 116-day growing season is longer than 30% 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 199 nights a year at or below 32°F.
- Compared with Great Falls, MT, 105 km away, the last frost here is 18 days later than there and the growing season is 32 days shorter.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | May 11 |
| 50% (median) | May 24 |
| 10% (safe for tender plants) | June 9 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | September 3 |
| 50% (median) | September 17 |
| 90% (late) | September 29 |
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 Chester, MT
Chester, MT frost dates — last frost May 24, first frost Sep 17, 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 23 to Aug 20
Start indoors: Mar 29 to Apr 12Transplant outside: Apr 26 to May 10Sow outdoors: Apr 26 to May 10Plant for fall: Jul 9 to Jul 30
Start indoors: Mar 29 to Apr 12Transplant outside: May 10 to May 24Plant for fall: Jun 11 to Jul 2
Start indoors: Mar 29 to Apr 12Transplant outside: May 3 to May 17Plant for fall: Jun 11 to Jul 2
Start indoors: Mar 29 to Apr 12Transplant outside: May 10 to May 24Plant for fall: Jun 11 to Jul 2
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 25 to Jul 16
Sow outdoors: Apr 12 to May 3Plant for fall: Jul 23 to Aug 13
Sow outdoors: Apr 19 to May 31Plant for fall: Aug 6 to Aug 27
Start indoors: Apr 26 to May 3Transplant outside: Jun 7 to Jun 14Sow outdoors: May 31 to Jun 14Plant for fall: Jul 2 to Jul 16
Start indoors: Apr 26 to May 3Sow outdoors: May 31 to Jun 14Plant for fall: Jul 9 to Jul 23
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 25 to Jul 9
Sow outdoors: May 3 to May 31Plant for fall: Jul 9 to Jul 23
Sow outdoors: May 3 to May 24
Sow outdoors: May 10 to Jun 7Plant for fall: Jul 9 to Jul 23
Sow outdoors: May 10 to May 31Plant for fall: Jul 23 to Aug 13
Sow outdoors: May 31 to Jun 21
Sow outdoors: May 31 to Jun 14
Transplant outside: Jun 7 to Jun 28
Plant for fall: Sep 3 to Oct 8
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Chester, 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 23 – Aug 20 |
| Kale | Mar 29 – Apr 12 | Apr 26 – May 10 | Apr 26 – May 10 | Jul 9 – Jul 30 |
| Broccoli | Mar 29 – Apr 12 | May 10 – May 24 | — | Jun 11 – Jul 2 |
| Cabbage | Mar 29 – Apr 12 | May 3 – May 17 | — | Jun 11 – Jul 2 |
| Cauliflower | Mar 29 – Apr 12 | May 10 – May 24 | — | Jun 11 – Jul 2 |
| 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 25 – Jul 16 |
| Spinach | — | — | Apr 12 – May 3 | Jul 23 – Aug 13 |
| Radishes | — | — | Apr 19 – May 31 | Aug 6 – Aug 27 |
| Cucumbers | Apr 26 – May 3 | Jun 7 – Jun 14 | May 31 – Jun 14 | Jul 2 – Jul 16 |
| Zucchini & Summer Squash | Apr 26 – May 3 | — | May 31 – Jun 14 | Jul 9 – Jul 23 |
| Winter Squash & Pumpkins | Apr 26 – May 3 | — | May 31 – Jun 14 | — |
| Melons & Watermelon | Apr 26 – May 3 | Jun 7 – Jun 21 | — | — |
| Carrots | — | — | May 3 – May 31 | Jun 25 – Jul 9 |
| Beets | — | — | May 3 – May 31 | Jul 9 – Jul 23 |
| Potatoes | — | — | May 3 – May 24 | — |
| Swiss Chard | — | — | May 10 – Jun 7 | Jul 9 – Jul 23 |
| Cilantro | — | — | May 10 – May 31 | Jul 23 – Aug 13 |
| Green Beans | — | — | May 31 – Jun 21 | — |
| Sweet Corn | — | — | May 31 – Jun 14 | — |
| Sweet Potatoes | — | Jun 7 – Jun 28 | — | — |
| Garlic | — | — | — | Sep 3 – Oct 8 |
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 Chester, MT weather station, 6 km away (elevation 3,133 ft (955 m)).
Frost dates near Chester
- Lothair May 24 · Sep 17
- Joplin May 21 · Sep 19
- Inverness May 21 · Sep 19
- Rudyard May 21 · Sep 19
- Ledger May 16 · Sep 23
- Hingham May 24 · Sep 15
- Whitlash frost any month
- Gildford May 24 · Sep 15
- Galata May 23 · Sep 14
- Shelby May 23 · Sep 16
Frequently asked questions
When is the last frost in Chester, MT?
The median last spring frost in Chester, MT is May 24. There is still about a 10% chance of frost after June 9, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Chester, MT?
The median first fall frost is September 17, with about a 10% chance of frost before September 3.
How long is the growing season in Chester, MT?
About 116 days between the median last spring frost and first fall frost.
What planting zone is Chester, MT?
Chester, MT is in USDA hardiness zone 4a.