Libby, MT frost dates
Last spring frostMay 10median date
First fall frostSep 26median date
Growing season139 daysfrost-free
Hardiness zone6aZone 6a
How Libby compares
- In 8 years out of 10, the last spring frost in Libby falls between April 28 and May 26, a 28-day window. The first fall frost falls between September 11 and October 12.
- The median last frost is 9 days earlier than the Montana median of May 19.
- Its 139-day growing season is longer than 79% of the 325 Montana places with a regular frost season (state median 125 days).
- The last frost is 11 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 182 nights a year at or below 32°F.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | April 28 |
| 50% (median) | May 10 |
| 10% (safe for tender plants) | May 26 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | September 11 |
| 50% (median) | September 26 |
| 90% (late) | October 12 |
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 Libby, MT
Libby, MT frost dates — last frost May 10, first frost Sep 26, zone 6a. whenisthelastfrost.com
Crop
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Start indoors: Feb 15 to Mar 1Transplant outside: Apr 12 to Apr 26
Start indoors: Mar 1 to Mar 15Transplant outside: May 24 to Jun 7
Start indoors: Mar 1 to Mar 15Transplant outside: May 24 to Jun 7
Start indoors: Mar 15 to Mar 29Transplant outside: May 17 to May 31
Start indoors: Mar 15 to Mar 29Transplant outside: Apr 19 to May 3Sow outdoors: Apr 12 to May 17Plant for fall: Aug 1 to Aug 29
Start indoors: Mar 15 to Mar 29Transplant outside: Apr 12 to Apr 26Sow outdoors: Apr 12 to Apr 26Plant for fall: Jul 18 to Aug 8
Start indoors: Mar 15 to Mar 29Transplant outside: Apr 26 to May 10Plant for fall: Jun 20 to Jul 11
Start indoors: Mar 15 to Mar 29Transplant outside: Apr 19 to May 3Plant for fall: Jun 20 to Jul 11
Start indoors: Mar 15 to Mar 29Transplant outside: Apr 26 to May 10Plant for fall: Jun 20 to Jul 11
Start indoors: Mar 29 to Apr 12Transplant outside: May 31 to Jun 14Sow outdoors: May 31 to Jun 14
Start indoors: Mar 29 to Apr 12Transplant outside: May 17 to May 31
Sow outdoors: Mar 29 to Apr 19Plant for fall: Jul 4 to Jul 25
Sow outdoors: Mar 29 to Apr 19Plant for fall: Aug 1 to Aug 22
Sow outdoors: Apr 5 to May 17Plant for fall: Aug 15 to Sep 5
Start indoors: Apr 12 to Apr 19Transplant outside: May 24 to May 31Sow outdoors: May 17 to May 31Plant for fall: Jul 11 to Jul 25
Start indoors: Apr 12 to Apr 19Sow outdoors: May 17 to May 31Plant for fall: Jul 18 to Aug 1
Start indoors: Apr 12 to Apr 19Sow outdoors: May 17 to May 31
Start indoors: Apr 12 to Apr 19Transplant outside: May 24 to Jun 7
Sow outdoors: Apr 19 to May 17Plant for fall: Jul 4 to Jul 18
Sow outdoors: Apr 19 to May 17Plant for fall: Jul 18 to Aug 1
Sow outdoors: Apr 19 to May 10
Sow outdoors: Apr 26 to May 24Plant for fall: Jul 18 to Aug 1
Sow outdoors: Apr 26 to May 17Plant for fall: Aug 1 to Aug 22
Sow outdoors: May 17 to Jun 7Plant for fall: Jul 11 to Jul 25
Sow outdoors: May 17 to May 31
Transplant outside: May 24 to Jun 14
Plant for fall: Sep 12 to Oct 17
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Libby, MT
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Feb 15 – Mar 1 | Apr 12 – Apr 26 | — | — |
| Peppers | Mar 1 – Mar 15 | May 24 – Jun 7 | — | — |
| Eggplant | Mar 1 – Mar 15 | May 24 – Jun 7 | — | — |
| Tomatoes | Mar 15 – Mar 29 | May 17 – May 31 | — | — |
| Lettuce | Mar 15 – Mar 29 | Apr 19 – May 3 | Apr 12 – May 17 | Aug 1 – Aug 29 |
| Kale | Mar 15 – Mar 29 | Apr 12 – Apr 26 | Apr 12 – Apr 26 | Jul 18 – Aug 8 |
| Broccoli | Mar 15 – Mar 29 | Apr 26 – May 10 | — | Jun 20 – Jul 11 |
| Cabbage | Mar 15 – Mar 29 | Apr 19 – May 3 | — | Jun 20 – Jul 11 |
| Cauliflower | Mar 15 – Mar 29 | Apr 26 – May 10 | — | Jun 20 – Jul 11 |
| Okra | Mar 29 – Apr 12 | May 31 – Jun 14 | May 31 – Jun 14 | — |
| Basil | Mar 29 – Apr 12 | May 17 – May 31 | — | — |
| Peas | — | — | Mar 29 – Apr 19 | Jul 4 – Jul 25 |
| Spinach | — | — | Mar 29 – Apr 19 | Aug 1 – Aug 22 |
| Radishes | — | — | Apr 5 – May 17 | Aug 15 – Sep 5 |
| Cucumbers | Apr 12 – Apr 19 | May 24 – May 31 | May 17 – May 31 | Jul 11 – Jul 25 |
| Zucchini & Summer Squash | Apr 12 – Apr 19 | — | May 17 – May 31 | Jul 18 – Aug 1 |
| Winter Squash & Pumpkins | Apr 12 – Apr 19 | — | May 17 – May 31 | — |
| Melons & Watermelon | Apr 12 – Apr 19 | May 24 – Jun 7 | — | — |
| Carrots | — | — | Apr 19 – May 17 | Jul 4 – Jul 18 |
| Beets | — | — | Apr 19 – May 17 | Jul 18 – Aug 1 |
| Potatoes | — | — | Apr 19 – May 10 | — |
| Swiss Chard | — | — | Apr 26 – May 24 | Jul 18 – Aug 1 |
| Cilantro | — | — | Apr 26 – May 17 | Aug 1 – Aug 22 |
| Green Beans | — | — | May 17 – Jun 7 | Jul 11 – Jul 25 |
| Sweet Corn | — | — | May 17 – May 31 | — |
| Sweet Potatoes | — | May 24 – Jun 14 | — | — |
| Garlic | — | — | — | Sep 12 – Oct 17 |
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 Libby, MT weather station, about 1 km away (elevation 2,139 ft (652 m)).
Frost dates near Libby
- Troy May 14 · Sep 25
- Noxon May 20 · Sep 20
- Heron May 20 · Sep 20
- Trego May 16 · Sep 18
- Trout Creek May 20 · Sep 21
- Fortine May 16 · Sep 18
- Rexford May 11 · Sep 27
- Eureka May 11 · Sep 27
- Stryker May 16 · Sep 18
- Marion frost any month
Frequently asked questions
When is the last frost in Libby, MT?
The median last spring frost in Libby, MT is May 10. 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 Libby, MT?
The median first fall frost is September 26, with about a 10% chance of frost before September 11.
How long is the growing season in Libby, MT?
About 139 days between the median last spring frost and first fall frost.
What planting zone is Libby, MT?
Libby, MT is in USDA hardiness zone 6a.