Saint Marie, MT frost dates
Last spring frostMay 13median date
First fall frostSep 27median date
Growing season137 daysfrost-free
Hardiness zone4aZone 4a
How Saint Marie compares
- In 8 years out of 10, the last spring frost in Saint Marie falls between May 2 and May 26, a 24-day window. The first fall frost falls between September 13 and October 9.
- The median last frost is 6 days earlier than the Montana median of May 19.
- Its 137-day growing season is longer than 77% 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 2 |
| 50% (median) | May 13 |
| 10% (safe for tender plants) | May 26 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | September 13 |
| 50% (median) | September 27 |
| 90% (late) | October 9 |
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 Saint Marie, MT
Saint Marie, MT frost dates — last frost May 13, first frost Sep 27, zone 4a. whenisthelastfrost.com
Crop
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Start indoors: Feb 18 to Mar 4Transplant outside: Apr 15 to Apr 29
Start indoors: Mar 4 to Mar 18Transplant outside: May 27 to Jun 10
Start indoors: Mar 4 to Mar 18Transplant outside: May 27 to Jun 10
Start indoors: Mar 18 to Apr 1Transplant outside: May 20 to Jun 3
Start indoors: Mar 18 to Apr 1Transplant outside: Apr 22 to May 6Sow outdoors: Apr 15 to May 20Plant for fall: Aug 2 to Aug 30
Start indoors: Mar 18 to Apr 1Transplant outside: Apr 15 to Apr 29Sow outdoors: Apr 15 to Apr 29Plant for fall: Jul 19 to Aug 9
Start indoors: Mar 18 to Apr 1Transplant outside: Apr 29 to May 13Plant for fall: Jun 21 to Jul 12
Start indoors: Mar 18 to Apr 1Transplant outside: Apr 22 to May 6Plant for fall: Jun 21 to Jul 12
Start indoors: Mar 18 to Apr 1Transplant outside: Apr 29 to May 13Plant for fall: Jun 21 to Jul 12
Start indoors: Apr 1 to Apr 15Transplant outside: Jun 3 to Jun 17Sow outdoors: Jun 3 to Jun 17
Start indoors: Apr 1 to Apr 15Transplant outside: May 20 to Jun 3
Sow outdoors: Apr 1 to Apr 22Plant for fall: Jul 5 to Jul 26
Sow outdoors: Apr 1 to Apr 22Plant for fall: Aug 2 to Aug 23
Sow outdoors: Apr 8 to May 20Plant for fall: Aug 16 to Sep 6
Start indoors: Apr 15 to Apr 22Transplant outside: May 27 to Jun 3Sow outdoors: May 20 to Jun 3Plant for fall: Jul 12 to Jul 26
Start indoors: Apr 15 to Apr 22Sow outdoors: May 20 to Jun 3Plant for fall: Jul 19 to Aug 2
Start indoors: Apr 15 to Apr 22Sow outdoors: May 20 to Jun 3
Start indoors: Apr 15 to Apr 22Transplant outside: May 27 to Jun 10
Sow outdoors: Apr 22 to May 20Plant for fall: Jul 5 to Jul 19
Sow outdoors: Apr 22 to May 20Plant for fall: Jul 19 to Aug 2
Sow outdoors: Apr 22 to May 13
Sow outdoors: Apr 29 to May 27Plant for fall: Jul 19 to Aug 2
Sow outdoors: Apr 29 to May 20Plant for fall: Aug 2 to Aug 23
Sow outdoors: May 20 to Jun 10Plant for fall: Jul 12 to Jul 26
Sow outdoors: May 20 to Jun 3
Transplant outside: May 27 to Jun 17
Plant for fall: Sep 13 to Oct 18
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Saint Marie, MT
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Feb 18 – Mar 4 | Apr 15 – Apr 29 | — | — |
| Peppers | Mar 4 – Mar 18 | May 27 – Jun 10 | — | — |
| Eggplant | Mar 4 – Mar 18 | May 27 – Jun 10 | — | — |
| Tomatoes | Mar 18 – Apr 1 | May 20 – Jun 3 | — | — |
| Lettuce | Mar 18 – Apr 1 | Apr 22 – May 6 | Apr 15 – May 20 | Aug 2 – Aug 30 |
| Kale | Mar 18 – Apr 1 | Apr 15 – Apr 29 | Apr 15 – Apr 29 | Jul 19 – Aug 9 |
| Broccoli | Mar 18 – Apr 1 | Apr 29 – May 13 | — | Jun 21 – Jul 12 |
| Cabbage | Mar 18 – Apr 1 | Apr 22 – May 6 | — | Jun 21 – Jul 12 |
| Cauliflower | Mar 18 – Apr 1 | Apr 29 – May 13 | — | Jun 21 – Jul 12 |
| Okra | Apr 1 – Apr 15 | Jun 3 – Jun 17 | Jun 3 – Jun 17 | — |
| Basil | Apr 1 – Apr 15 | May 20 – Jun 3 | — | — |
| Peas | — | — | Apr 1 – Apr 22 | Jul 5 – Jul 26 |
| Spinach | — | — | Apr 1 – Apr 22 | Aug 2 – Aug 23 |
| Radishes | — | — | Apr 8 – May 20 | Aug 16 – Sep 6 |
| Cucumbers | Apr 15 – Apr 22 | May 27 – Jun 3 | May 20 – Jun 3 | Jul 12 – Jul 26 |
| Zucchini & Summer Squash | Apr 15 – Apr 22 | — | May 20 – Jun 3 | Jul 19 – Aug 2 |
| Winter Squash & Pumpkins | Apr 15 – Apr 22 | — | May 20 – Jun 3 | — |
| Melons & Watermelon | Apr 15 – Apr 22 | May 27 – Jun 10 | — | — |
| Carrots | — | — | Apr 22 – May 20 | Jul 5 – Jul 19 |
| Beets | — | — | Apr 22 – May 20 | Jul 19 – Aug 2 |
| Potatoes | — | — | Apr 22 – May 13 | — |
| Swiss Chard | — | — | Apr 29 – May 27 | Jul 19 – Aug 2 |
| Cilantro | — | — | Apr 29 – May 20 | Aug 2 – Aug 23 |
| Green Beans | — | — | May 20 – Jun 10 | Jul 12 – Jul 26 |
| Sweet Corn | — | — | May 20 – Jun 3 | — |
| Sweet Potatoes | — | May 27 – Jun 17 | — | — |
| Garlic | — | — | — | Sep 13 – Oct 18 |
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 St Marie, MT weather station, 2 km away (elevation 2,756 ft (840 m)).
Frost dates near Saint Marie
- Glasgow May 6 · Sep 30
- Larslan Jun 5 · Sep 2
- Vandalia May 15 · Sep 26
- Nashua May 12 · Sep 24
- Hinsdale May 15 · Sep 26
- Frazer May 12 · Sep 24
- Richland Jun 5 · Sep 2
- Fort Peck May 8 · Oct 1
- Opheim Jun 1 · Sep 7
- Glentana Jun 5 · Sep 2
Frequently asked questions
When is the last frost in Saint Marie, MT?
The median last spring frost in Saint Marie, MT is May 13. There is still about a 10% chance of frost after May 26, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Saint Marie, MT?
The median first fall frost is September 27, with about a 10% chance of frost before September 13.
How long is the growing season in Saint Marie, MT?
About 137 days between the median last spring frost and first fall frost.
What planting zone is Saint Marie, MT?
Saint Marie, MT is in USDA hardiness zone 4a.