Inverness, MT frost dates
Last spring frostMay 21median date
First fall frostSep 19median date
Growing season121 daysfrost-free
Hardiness zone4aZone 4a
How Inverness compares
- In 8 years out of 10, the last spring frost in Inverness falls between May 8 and June 6, a 29-day window. The first fall frost falls between September 3 and October 1.
- The median last frost is 2 days later than the Montana median of May 19.
- Its 121-day growing season is longer than 35% of the 325 Montana places with a regular frost season (state median 125 days).
- The last frost is 9 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 189 nights a year at or below 32°F.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | May 8 |
| 50% (median) | May 21 |
| 10% (safe for tender plants) | June 6 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | September 3 |
| 50% (median) | September 19 |
| 90% (late) | October 1 |
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 Inverness, MT
Inverness, MT frost dates — last frost May 21, first frost Sep 19, zone 4a. whenisthelastfrost.com
Crop
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Start indoors: Feb 26 to Mar 12Transplant outside: Apr 23 to May 7
Start indoors: Mar 12 to Mar 26Transplant outside: Jun 4 to Jun 18
Start indoors: Mar 12 to Mar 26Transplant outside: Jun 4 to Jun 18
Start indoors: Mar 26 to Apr 9Transplant outside: May 28 to Jun 11
Start indoors: Mar 26 to Apr 9Transplant outside: Apr 30 to May 14Sow outdoors: Apr 23 to May 28Plant for fall: Jul 25 to Aug 22
Start indoors: Mar 26 to Apr 9Transplant outside: Apr 23 to May 7Sow outdoors: Apr 23 to May 7Plant for fall: Jul 11 to Aug 1
Start indoors: Mar 26 to Apr 9Transplant outside: May 7 to May 21Plant for fall: Jun 13 to Jul 4
Start indoors: Mar 26 to Apr 9Transplant outside: Apr 30 to May 14Plant for fall: Jun 13 to Jul 4
Start indoors: Mar 26 to Apr 9Transplant outside: May 7 to May 21Plant for fall: Jun 13 to Jul 4
Start indoors: Apr 9 to Apr 23Transplant outside: Jun 11 to Jun 25Sow outdoors: Jun 11 to Jun 25
Start indoors: Apr 9 to Apr 23Transplant outside: May 28 to Jun 11
Sow outdoors: Apr 9 to Apr 30Plant for fall: Jun 27 to Jul 18
Sow outdoors: Apr 9 to Apr 30Plant for fall: Jul 25 to Aug 15
Sow outdoors: Apr 16 to May 28Plant for fall: Aug 8 to Aug 29
Start indoors: Apr 23 to Apr 30Transplant outside: Jun 4 to Jun 11Sow outdoors: May 28 to Jun 11Plant for fall: Jul 4 to Jul 18
Start indoors: Apr 23 to Apr 30Sow outdoors: May 28 to Jun 11Plant for fall: Jul 11 to Jul 25
Start indoors: Apr 23 to Apr 30Sow outdoors: May 28 to Jun 11
Start indoors: Apr 23 to Apr 30Transplant outside: Jun 4 to Jun 18
Sow outdoors: Apr 30 to May 28Plant for fall: Jun 27 to Jul 11
Sow outdoors: Apr 30 to May 28Plant for fall: Jul 11 to Jul 25
Sow outdoors: Apr 30 to May 21
Sow outdoors: May 7 to Jun 4Plant for fall: Jul 11 to Jul 25
Sow outdoors: May 7 to May 28Plant for fall: Jul 25 to Aug 15
Sow outdoors: May 28 to Jun 18Plant for fall: Jul 4 to Jul 18
Sow outdoors: May 28 to Jun 11
Transplant outside: Jun 4 to Jun 25
Plant for fall: Sep 5 to Oct 10
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Inverness, MT
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Feb 26 – Mar 12 | Apr 23 – May 7 | — | — |
| Peppers | Mar 12 – Mar 26 | Jun 4 – Jun 18 | — | — |
| Eggplant | Mar 12 – Mar 26 | Jun 4 – Jun 18 | — | — |
| Tomatoes | Mar 26 – Apr 9 | May 28 – Jun 11 | — | — |
| Lettuce | Mar 26 – Apr 9 | Apr 30 – May 14 | Apr 23 – May 28 | Jul 25 – Aug 22 |
| Kale | Mar 26 – Apr 9 | Apr 23 – May 7 | Apr 23 – May 7 | Jul 11 – Aug 1 |
| Broccoli | Mar 26 – Apr 9 | May 7 – May 21 | — | Jun 13 – Jul 4 |
| Cabbage | Mar 26 – Apr 9 | Apr 30 – May 14 | — | Jun 13 – Jul 4 |
| Cauliflower | Mar 26 – Apr 9 | May 7 – May 21 | — | Jun 13 – Jul 4 |
| Okra | Apr 9 – Apr 23 | Jun 11 – Jun 25 | Jun 11 – Jun 25 | — |
| Basil | Apr 9 – Apr 23 | May 28 – Jun 11 | — | — |
| Peas | — | — | Apr 9 – Apr 30 | Jun 27 – Jul 18 |
| Spinach | — | — | Apr 9 – Apr 30 | Jul 25 – Aug 15 |
| Radishes | — | — | Apr 16 – May 28 | Aug 8 – Aug 29 |
| Cucumbers | Apr 23 – Apr 30 | Jun 4 – Jun 11 | May 28 – Jun 11 | Jul 4 – Jul 18 |
| Zucchini & Summer Squash | Apr 23 – Apr 30 | — | May 28 – Jun 11 | Jul 11 – Jul 25 |
| Winter Squash & Pumpkins | Apr 23 – Apr 30 | — | May 28 – Jun 11 | — |
| Melons & Watermelon | Apr 23 – Apr 30 | Jun 4 – Jun 18 | — | — |
| Carrots | — | — | Apr 30 – May 28 | Jun 27 – Jul 11 |
| Beets | — | — | Apr 30 – May 28 | Jul 11 – Jul 25 |
| Potatoes | — | — | Apr 30 – May 21 | — |
| Swiss Chard | — | — | May 7 – Jun 4 | Jul 11 – Jul 25 |
| Cilantro | — | — | May 7 – May 28 | Jul 25 – Aug 15 |
| Green Beans | — | — | May 28 – Jun 18 | Jul 4 – Jul 18 |
| Sweet Corn | — | — | May 28 – Jun 11 | — |
| Sweet Potatoes | — | Jun 4 – Jun 25 | — | — |
| Garlic | — | — | — | Sep 5 – Oct 10 |
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 Joplin, MT weather station, 7 km away (elevation 3,323 ft (1,013 m)).
Frost dates near Inverness
- Rudyard May 21 · Sep 19
- Joplin May 21 · Sep 19
- Hingham May 24 · Sep 15
- Chester May 24 · Sep 17
- Gildford May 24 · Sep 15
- Lothair May 24 · Sep 17
- Whitlash frost any month
- Kremlin May 24 · Sep 15
- Galata May 23 · Sep 14
- Ledger May 16 · Sep 23
Frequently asked questions
When is the last frost in Inverness, MT?
The median last spring frost in Inverness, MT is May 21. There is still about a 10% chance of frost after June 6, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Inverness, MT?
The median first fall frost is September 19, with about a 10% chance of frost before September 3.
How long is the growing season in Inverness, MT?
About 121 days between the median last spring frost and first fall frost.
What planting zone is Inverness, MT?
Inverness, MT is in USDA hardiness zone 4a.