Box Elder, MT frost dates
Last spring frostMay 15median date
First fall frostSep 24median date
Growing season132 daysfrost-free
Hardiness zone4aZone 4a
How Box Elder compares
- In 8 years out of 10, the last spring frost in Box Elder falls between May 4 and May 28, a 24-day window. The first fall frost falls between September 8 and October 4.
- The median last frost is 4 days earlier than the Montana median of May 19.
- Its 132-day growing season is longer than 64% of the 325 Montana places with a regular frost season (state median 125 days).
- The last frost is typical for zone 4a, where the median is May 12.
- The weather station records an average of 179 nights a year at or below 32°F.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | May 4 |
| 50% (median) | May 15 |
| 10% (safe for tender plants) | May 28 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | September 8 |
| 50% (median) | September 24 |
| 90% (late) | October 4 |
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 Box Elder, MT
Box Elder, MT frost dates — last frost May 15, first frost Sep 24, zone 4a. whenisthelastfrost.com
Crop
JFMAMJJASOND
Start indoors: Feb 20 to Mar 6Transplant outside: Apr 17 to May 1
Start indoors: Mar 6 to Mar 20Transplant outside: May 29 to Jun 12
Start indoors: Mar 6 to Mar 20Transplant outside: May 29 to Jun 12
Start indoors: Mar 20 to Apr 3Transplant outside: May 22 to Jun 5
Start indoors: Mar 20 to Apr 3Transplant outside: Apr 24 to May 8Sow outdoors: Apr 17 to May 22Plant for fall: Jul 30 to Aug 27
Start indoors: Mar 20 to Apr 3Transplant outside: Apr 17 to May 1Sow outdoors: Apr 17 to May 1Plant for fall: Jul 16 to Aug 6
Start indoors: Mar 20 to Apr 3Transplant outside: May 1 to May 15Plant for fall: Jun 18 to Jul 9
Start indoors: Mar 20 to Apr 3Transplant outside: Apr 24 to May 8Plant for fall: Jun 18 to Jul 9
Start indoors: Mar 20 to Apr 3Transplant outside: May 1 to May 15Plant for fall: Jun 18 to Jul 9
Start indoors: Apr 3 to Apr 17Transplant outside: Jun 5 to Jun 19Sow outdoors: Jun 5 to Jun 19
Start indoors: Apr 3 to Apr 17Transplant outside: May 22 to Jun 5
Sow outdoors: Apr 3 to Apr 24Plant for fall: Jul 2 to Jul 23
Sow outdoors: Apr 3 to Apr 24Plant for fall: Jul 30 to Aug 20
Sow outdoors: Apr 10 to May 22Plant for fall: Aug 13 to Sep 3
Start indoors: Apr 17 to Apr 24Transplant outside: May 29 to Jun 5Sow outdoors: May 22 to Jun 5Plant for fall: Jul 9 to Jul 23
Start indoors: Apr 17 to Apr 24Sow outdoors: May 22 to Jun 5Plant for fall: Jul 16 to Jul 30
Start indoors: Apr 17 to Apr 24Sow outdoors: May 22 to Jun 5
Start indoors: Apr 17 to Apr 24Transplant outside: May 29 to Jun 12
Sow outdoors: Apr 24 to May 22Plant for fall: Jul 2 to Jul 16
Sow outdoors: Apr 24 to May 22Plant for fall: Jul 16 to Jul 30
Sow outdoors: Apr 24 to May 15
Sow outdoors: May 1 to May 29Plant for fall: Jul 16 to Jul 30
Sow outdoors: May 1 to May 22Plant for fall: Jul 30 to Aug 20
Sow outdoors: May 22 to Jun 12Plant for fall: Jul 9 to Jul 23
Sow outdoors: May 22 to Jun 5
Transplant outside: May 29 to Jun 19
Plant for fall: Sep 10 to Oct 15
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Box Elder, MT
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Feb 20 – Mar 6 | Apr 17 – May 1 | — | — |
| Peppers | Mar 6 – Mar 20 | May 29 – Jun 12 | — | — |
| Eggplant | Mar 6 – Mar 20 | May 29 – Jun 12 | — | — |
| Tomatoes | Mar 20 – Apr 3 | May 22 – Jun 5 | — | — |
| Lettuce | Mar 20 – Apr 3 | Apr 24 – May 8 | Apr 17 – May 22 | Jul 30 – Aug 27 |
| Kale | Mar 20 – Apr 3 | Apr 17 – May 1 | Apr 17 – May 1 | Jul 16 – Aug 6 |
| Broccoli | Mar 20 – Apr 3 | May 1 – May 15 | — | Jun 18 – Jul 9 |
| Cabbage | Mar 20 – Apr 3 | Apr 24 – May 8 | — | Jun 18 – Jul 9 |
| Cauliflower | Mar 20 – Apr 3 | May 1 – May 15 | — | Jun 18 – Jul 9 |
| Okra | Apr 3 – Apr 17 | Jun 5 – Jun 19 | Jun 5 – Jun 19 | — |
| Basil | Apr 3 – Apr 17 | May 22 – Jun 5 | — | — |
| Peas | — | — | Apr 3 – Apr 24 | Jul 2 – Jul 23 |
| Spinach | — | — | Apr 3 – Apr 24 | Jul 30 – Aug 20 |
| Radishes | — | — | Apr 10 – May 22 | Aug 13 – Sep 3 |
| Cucumbers | Apr 17 – Apr 24 | May 29 – Jun 5 | May 22 – Jun 5 | Jul 9 – Jul 23 |
| Zucchini & Summer Squash | Apr 17 – Apr 24 | — | May 22 – Jun 5 | Jul 16 – Jul 30 |
| Winter Squash & Pumpkins | Apr 17 – Apr 24 | — | May 22 – Jun 5 | — |
| Melons & Watermelon | Apr 17 – Apr 24 | May 29 – Jun 12 | — | — |
| Carrots | — | — | Apr 24 – May 22 | Jul 2 – Jul 16 |
| Beets | — | — | Apr 24 – May 22 | Jul 16 – Jul 30 |
| Potatoes | — | — | Apr 24 – May 15 | — |
| Swiss Chard | — | — | May 1 – May 29 | Jul 16 – Jul 30 |
| Cilantro | — | — | May 1 – May 22 | Jul 30 – Aug 20 |
| Green Beans | — | — | May 22 – Jun 12 | Jul 9 – Jul 23 |
| Sweet Corn | — | — | May 22 – Jun 5 | — |
| Sweet Potatoes | — | May 29 – Jun 19 | — | — |
| Garlic | — | — | — | Sep 10 – Oct 15 |
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 Ft Assiniboine, MT weather station, 24 km away (elevation 2,674 ft (815 m)).
Frost dates near Box Elder
- Big Sandy May 17 · Sep 25
- Havre May 15 · Sep 23
- Kremlin May 24 · Sep 15
- Gildford May 24 · Sep 15
- Lloyd May 23 · Sep 23
- Chinook May 14 · Sep 23
- Hingham May 24 · Sep 15
- Loma May 20 · Sep 19
- Rudyard May 21 · Sep 19
- Zurich May 14 · Sep 23
Frequently asked questions
When is the last frost in Box Elder, MT?
The median last spring frost in Box Elder, MT is May 15. There is still about a 10% chance of frost after May 28, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Box Elder, MT?
The median first fall frost is September 24, with about a 10% chance of frost before September 8.
How long is the growing season in Box Elder, MT?
About 132 days between the median last spring frost and first fall frost.
What planting zone is Box Elder, MT?
Box Elder, MT is in USDA hardiness zone 4a.