Saint Ignatius, MT frost dates
Last spring frostMay 12median date
First fall frostOct 2median date
Growing season143 daysfrost-free
Hardiness zone6aZone 6a
How Saint Ignatius compares
- In 8 years out of 10, the last spring frost in Saint Ignatius falls between April 28 and June 1, a 34-day window. The first fall frost falls between September 19 and October 14.
- The median last frost is 7 days earlier than the Montana median of May 19.
- Its 143-day growing season is longer than 85% of the 325 Montana places with a regular frost season (state median 125 days).
- The last frost is 13 days later than the zone 6a median of Apr 29. Hardiness zones measure winter cold, not season length, so use these dates rather than a zone 6a chart.
- The weather station records an average of 152 nights a year at or below 32°F.
- Compared with Missoula, MT, 50 km away, the last frost here is 2 days later than there and the growing season is 1 day shorter.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | April 28 |
| 50% (median) | May 12 |
| 10% (safe for tender plants) | June 1 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | September 19 |
| 50% (median) | October 2 |
| 90% (late) | October 14 |
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 Ignatius, MT
Saint Ignatius, MT frost dates — last frost May 12, first frost Oct 2, zone 6a. whenisthelastfrost.com
Crop
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Start indoors: Feb 17 to Mar 3Transplant outside: Apr 14 to Apr 28
Start indoors: Mar 3 to Mar 17Transplant outside: May 26 to Jun 9
Start indoors: Mar 3 to Mar 17Transplant outside: May 26 to Jun 9
Start indoors: Mar 17 to Mar 31Transplant outside: May 19 to Jun 2
Start indoors: Mar 17 to Mar 31Transplant outside: Apr 21 to May 5Sow outdoors: Apr 14 to May 19Plant for fall: Aug 7 to Sep 4
Start indoors: Mar 17 to Mar 31Transplant outside: Apr 14 to Apr 28Sow outdoors: Apr 14 to Apr 28Plant for fall: Jul 24 to Aug 14
Start indoors: Mar 17 to Mar 31Transplant outside: Apr 28 to May 12Plant for fall: Jun 26 to Jul 17
Start indoors: Mar 17 to Mar 31Transplant outside: Apr 21 to May 5Plant for fall: Jun 26 to Jul 17
Start indoors: Mar 17 to Mar 31Transplant outside: Apr 28 to May 12Plant for fall: Jun 26 to Jul 17
Start indoors: Mar 31 to Apr 14Transplant outside: Jun 2 to Jun 16Sow outdoors: Jun 2 to Jun 16
Start indoors: Mar 31 to Apr 14Transplant outside: May 19 to Jun 2
Sow outdoors: Mar 31 to Apr 21Plant for fall: Jul 10 to Jul 31
Sow outdoors: Mar 31 to Apr 21Plant for fall: Aug 7 to Aug 28
Sow outdoors: Apr 7 to May 19Plant for fall: Aug 21 to Sep 11
Start indoors: Apr 14 to Apr 21Transplant outside: May 26 to Jun 2Sow outdoors: May 19 to Jun 2Plant for fall: Jul 17 to Jul 31
Start indoors: Apr 14 to Apr 21Sow outdoors: May 19 to Jun 2Plant for fall: Jul 24 to Aug 7
Start indoors: Apr 14 to Apr 21Sow outdoors: May 19 to Jun 2
Start indoors: Apr 14 to Apr 21Transplant outside: May 26 to Jun 9
Sow outdoors: Apr 21 to May 19Plant for fall: Jul 10 to Jul 24
Sow outdoors: Apr 21 to May 19Plant for fall: Jul 24 to Aug 7
Sow outdoors: Apr 21 to May 12
Sow outdoors: Apr 28 to May 26Plant for fall: Jul 24 to Aug 7
Sow outdoors: Apr 28 to May 19Plant for fall: Aug 7 to Aug 28
Sow outdoors: May 19 to Jun 9Plant for fall: Jul 17 to Jul 31
Sow outdoors: May 19 to Jun 2
Transplant outside: May 26 to Jun 16
Plant for fall: Sep 18 to Oct 23
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Saint Ignatius, MT
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Feb 17 – Mar 3 | Apr 14 – Apr 28 | — | — |
| Peppers | Mar 3 – Mar 17 | May 26 – Jun 9 | — | — |
| Eggplant | Mar 3 – Mar 17 | May 26 – Jun 9 | — | — |
| Tomatoes | Mar 17 – Mar 31 | May 19 – Jun 2 | — | — |
| Lettuce | Mar 17 – Mar 31 | Apr 21 – May 5 | Apr 14 – May 19 | Aug 7 – Sep 4 |
| Kale | Mar 17 – Mar 31 | Apr 14 – Apr 28 | Apr 14 – Apr 28 | Jul 24 – Aug 14 |
| Broccoli | Mar 17 – Mar 31 | Apr 28 – May 12 | — | Jun 26 – Jul 17 |
| Cabbage | Mar 17 – Mar 31 | Apr 21 – May 5 | — | Jun 26 – Jul 17 |
| Cauliflower | Mar 17 – Mar 31 | Apr 28 – May 12 | — | Jun 26 – Jul 17 |
| Okra | Mar 31 – Apr 14 | Jun 2 – Jun 16 | Jun 2 – Jun 16 | — |
| Basil | Mar 31 – Apr 14 | May 19 – Jun 2 | — | — |
| Peas | — | — | Mar 31 – Apr 21 | Jul 10 – Jul 31 |
| Spinach | — | — | Mar 31 – Apr 21 | Aug 7 – Aug 28 |
| Radishes | — | — | Apr 7 – May 19 | Aug 21 – Sep 11 |
| Cucumbers | Apr 14 – Apr 21 | May 26 – Jun 2 | May 19 – Jun 2 | Jul 17 – Jul 31 |
| Zucchini & Summer Squash | Apr 14 – Apr 21 | — | May 19 – Jun 2 | Jul 24 – Aug 7 |
| Winter Squash & Pumpkins | Apr 14 – Apr 21 | — | May 19 – Jun 2 | — |
| Melons & Watermelon | Apr 14 – Apr 21 | May 26 – Jun 9 | — | — |
| Carrots | — | — | Apr 21 – May 19 | Jul 10 – Jul 24 |
| Beets | — | — | Apr 21 – May 19 | Jul 24 – Aug 7 |
| Potatoes | — | — | Apr 21 – May 12 | — |
| Swiss Chard | — | — | Apr 28 – May 26 | Jul 24 – Aug 7 |
| Cilantro | — | — | Apr 28 – May 19 | Aug 7 – Aug 28 |
| Green Beans | — | — | May 19 – Jun 9 | Jul 17 – Jul 31 |
| Sweet Corn | — | — | May 19 – Jun 2 | — |
| Sweet Potatoes | — | May 26 – Jun 16 | — | — |
| Garlic | — | — | — | Sep 18 – Oct 23 |
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 Saint Ignatius, MT weather station, 2 km away (elevation 2,917 ft (889 m)).
Frost dates near Saint Ignatius
- Ravalli May 12 · Oct 2
- Charlo May 12 · Oct 2
- Arlee May 12 · Oct 2
- Dixon May 12 · Oct 2
- Ronan May 10 · Oct 5
- Pablo May 10 · Oct 5
- Condon May 20 · Sep 22
- Frenchtown May 18 · Sep 25
- Huson May 18 · Sep 25
- Polson May 10 · Oct 5
Frequently asked questions
When is the last frost in Saint Ignatius, MT?
The median last spring frost in Saint Ignatius, MT is May 12. There is still about a 10% chance of frost after June 1, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Saint Ignatius, MT?
The median first fall frost is October 2, with about a 10% chance of frost before September 19.
How long is the growing season in Saint Ignatius, MT?
About 143 days between the median last spring frost and first fall frost.
What planting zone is Saint Ignatius, MT?
Saint Ignatius, MT is in USDA hardiness zone 6a.