Lewistown, MT frost dates
Last spring frostMay 14median date
First fall frostSep 28median date
Growing season137 daysfrost-free
Hardiness zone4bZone 4b
How Lewistown compares
- In 8 years out of 10, the last spring frost in Lewistown falls between May 2 and May 27, a 25-day window. The first fall frost falls between September 14 and October 10.
- The median last frost is 5 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 6 days later than the zone 4b median of May 8. Hardiness zones measure winter cold, not season length, so use these dates rather than a zone 4b chart.
- The weather station records an average of 166 nights a year at or below 32°F.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | May 2 |
| 50% (median) | May 14 |
| 10% (safe for tender plants) | May 27 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | September 14 |
| 50% (median) | September 28 |
| 90% (late) | October 10 |
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 Lewistown, MT
Lewistown, MT frost dates — last frost May 14, first frost Sep 28, zone 4b. whenisthelastfrost.com
Crop
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Start indoors: Feb 19 to Mar 5Transplant outside: Apr 16 to Apr 30
Start indoors: Mar 5 to Mar 19Transplant outside: May 28 to Jun 11
Start indoors: Mar 5 to Mar 19Transplant outside: May 28 to Jun 11
Start indoors: Mar 19 to Apr 2Transplant outside: May 21 to Jun 4
Start indoors: Mar 19 to Apr 2Transplant outside: Apr 23 to May 7Sow outdoors: Apr 16 to May 21Plant for fall: Aug 3 to Aug 31
Start indoors: Mar 19 to Apr 2Transplant outside: Apr 16 to Apr 30Sow outdoors: Apr 16 to Apr 30Plant for fall: Jul 20 to Aug 10
Start indoors: Mar 19 to Apr 2Transplant outside: Apr 30 to May 14Plant for fall: Jun 22 to Jul 13
Start indoors: Mar 19 to Apr 2Transplant outside: Apr 23 to May 7Plant for fall: Jun 22 to Jul 13
Start indoors: Mar 19 to Apr 2Transplant outside: Apr 30 to May 14Plant for fall: Jun 22 to Jul 13
Start indoors: Apr 2 to Apr 16Transplant outside: Jun 4 to Jun 18Sow outdoors: Jun 4 to Jun 18
Start indoors: Apr 2 to Apr 16Transplant outside: May 21 to Jun 4
Sow outdoors: Apr 2 to Apr 23Plant for fall: Jul 6 to Jul 27
Sow outdoors: Apr 2 to Apr 23Plant for fall: Aug 3 to Aug 24
Sow outdoors: Apr 9 to May 21Plant for fall: Aug 17 to Sep 7
Start indoors: Apr 16 to Apr 23Transplant outside: May 28 to Jun 4Sow outdoors: May 21 to Jun 4Plant for fall: Jul 13 to Jul 27
Start indoors: Apr 16 to Apr 23Sow outdoors: May 21 to Jun 4Plant for fall: Jul 20 to Aug 3
Start indoors: Apr 16 to Apr 23Sow outdoors: May 21 to Jun 4
Start indoors: Apr 16 to Apr 23Transplant outside: May 28 to Jun 11
Sow outdoors: Apr 23 to May 21Plant for fall: Jul 6 to Jul 20
Sow outdoors: Apr 23 to May 21Plant for fall: Jul 20 to Aug 3
Sow outdoors: Apr 23 to May 14
Sow outdoors: Apr 30 to May 28Plant for fall: Jul 20 to Aug 3
Sow outdoors: Apr 30 to May 21Plant for fall: Aug 3 to Aug 24
Sow outdoors: May 21 to Jun 11Plant for fall: Jul 13 to Jul 27
Sow outdoors: May 21 to Jun 4
Transplant outside: May 28 to Jun 18
Plant for fall: Sep 14 to Oct 19
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Lewistown, MT
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Feb 19 – Mar 5 | Apr 16 – Apr 30 | — | — |
| Peppers | Mar 5 – Mar 19 | May 28 – Jun 11 | — | — |
| Eggplant | Mar 5 – Mar 19 | May 28 – Jun 11 | — | — |
| Tomatoes | Mar 19 – Apr 2 | May 21 – Jun 4 | — | — |
| Lettuce | Mar 19 – Apr 2 | Apr 23 – May 7 | Apr 16 – May 21 | Aug 3 – Aug 31 |
| Kale | Mar 19 – Apr 2 | Apr 16 – Apr 30 | Apr 16 – Apr 30 | Jul 20 – Aug 10 |
| Broccoli | Mar 19 – Apr 2 | Apr 30 – May 14 | — | Jun 22 – Jul 13 |
| Cabbage | Mar 19 – Apr 2 | Apr 23 – May 7 | — | Jun 22 – Jul 13 |
| Cauliflower | Mar 19 – Apr 2 | Apr 30 – May 14 | — | Jun 22 – Jul 13 |
| Okra | Apr 2 – Apr 16 | Jun 4 – Jun 18 | Jun 4 – Jun 18 | — |
| Basil | Apr 2 – Apr 16 | May 21 – Jun 4 | — | — |
| Peas | — | — | Apr 2 – Apr 23 | Jul 6 – Jul 27 |
| Spinach | — | — | Apr 2 – Apr 23 | Aug 3 – Aug 24 |
| Radishes | — | — | Apr 9 – May 21 | Aug 17 – Sep 7 |
| Cucumbers | Apr 16 – Apr 23 | May 28 – Jun 4 | May 21 – Jun 4 | Jul 13 – Jul 27 |
| Zucchini & Summer Squash | Apr 16 – Apr 23 | — | May 21 – Jun 4 | Jul 20 – Aug 3 |
| Winter Squash & Pumpkins | Apr 16 – Apr 23 | — | May 21 – Jun 4 | — |
| Melons & Watermelon | Apr 16 – Apr 23 | May 28 – Jun 11 | — | — |
| Carrots | — | — | Apr 23 – May 21 | Jul 6 – Jul 20 |
| Beets | — | — | Apr 23 – May 21 | Jul 20 – Aug 3 |
| Potatoes | — | — | Apr 23 – May 14 | — |
| Swiss Chard | — | — | Apr 30 – May 28 | Jul 20 – Aug 3 |
| Cilantro | — | — | Apr 30 – May 21 | Aug 3 – Aug 24 |
| Green Beans | — | — | May 21 – Jun 11 | Jul 13 – Jul 27 |
| Sweet Corn | — | — | May 21 – Jun 4 | — |
| Sweet Potatoes | — | May 28 – Jun 18 | — | — |
| Garlic | — | — | — | Sep 14 – Oct 19 |
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 Lewistown, MT weather station, 2 km away (elevation 3,911 ft (1,192 m)).
Frost dates near Lewistown
- Hilger May 14 · Sep 28
- Moore May 23 · Sep 21
- Forest Grove May 19 · Sep 25
- Hobson May 28 · Sep 20
- Moccasin May 28 · Sep 20
- Buffalo Jun 1 · Sep 15
- Grass Range May 20 · Sep 24
- Denton Jun 1 · Sep 11
- Judith Gap Jun 1 · Sep 15
- Roy May 14 · Sep 24
Frequently asked questions
When is the last frost in Lewistown, MT?
The median last spring frost in Lewistown, MT is May 14. There is still about a 10% chance of frost after May 27, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Lewistown, MT?
The median first fall frost is September 28, with about a 10% chance of frost before September 14.
How long is the growing season in Lewistown, MT?
About 137 days between the median last spring frost and first fall frost.
What planting zone is Lewistown, MT?
Lewistown, MT is in USDA hardiness zone 4b.