Acton, MT frost dates
Last spring frostMay 4median date
First fall frostOct 7median date
Growing season156 daysfrost-free
Hardiness zone5aZone 5a
How Acton compares
- In 8 years out of 10, the last spring frost in Acton falls between April 20 and May 18, a 28-day window. The first fall frost falls between September 26 and October 21.
- The median last frost is 15 days earlier than the Montana median of May 19.
- Its 156-day growing season is among the longest of the 325 Montana places with a regular frost season.
- The last frost is typical for zone 5a, where the median is May 3.
- The weather station records an average of 142 nights a year at or below 32°F.
- Acton shares its weather station with Billings, MT, 20 km away, so the two have the same frost dates.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | April 20 |
| 50% (median) | May 4 |
| 10% (safe for tender plants) | May 18 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | September 26 |
| 50% (median) | October 7 |
| 90% (late) | October 21 |
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 Acton, MT
Acton, MT frost dates — last frost May 4, first frost Oct 7, zone 5a. whenisthelastfrost.com
Crop
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Start indoors: Feb 9 to Feb 23Transplant outside: Apr 6 to Apr 20
Start indoors: Feb 23 to Mar 9Transplant outside: May 18 to Jun 1
Start indoors: Feb 23 to Mar 9Transplant outside: May 18 to Jun 1
Start indoors: Mar 9 to Mar 23Transplant outside: May 11 to May 25
Start indoors: Mar 9 to Mar 23Transplant outside: Apr 13 to Apr 27Sow outdoors: Apr 6 to May 11Plant for fall: Aug 12 to Sep 9
Start indoors: Mar 9 to Mar 23Transplant outside: Apr 6 to Apr 20Sow outdoors: Apr 6 to Apr 20Plant for fall: Jul 29 to Aug 19
Start indoors: Mar 9 to Mar 23Transplant outside: Apr 20 to May 4Plant for fall: Jul 1 to Jul 22
Start indoors: Mar 9 to Mar 23Transplant outside: Apr 13 to Apr 27Plant for fall: Jul 1 to Jul 22
Start indoors: Mar 9 to Mar 23Transplant outside: Apr 20 to May 4Plant for fall: Jul 1 to Jul 22
Start indoors: Mar 23 to Apr 6Transplant outside: May 25 to Jun 8Sow outdoors: May 25 to Jun 8
Start indoors: Mar 23 to Apr 6Transplant outside: May 11 to May 25
Sow outdoors: Mar 23 to Apr 13Plant for fall: Jul 15 to Aug 5
Sow outdoors: Mar 23 to Apr 13Plant for fall: Aug 12 to Sep 2
Sow outdoors: Mar 30 to May 11Plant for fall: Aug 26 to Sep 16
Start indoors: Apr 6 to Apr 13Transplant outside: May 18 to May 25Sow outdoors: May 11 to May 25Plant for fall: Jul 22 to Aug 5
Start indoors: Apr 6 to Apr 13Sow outdoors: May 11 to May 25Plant for fall: Jul 29 to Aug 12
Start indoors: Apr 6 to Apr 13Sow outdoors: May 11 to May 25
Start indoors: Apr 6 to Apr 13Transplant outside: May 18 to Jun 1
Sow outdoors: Apr 13 to May 11Plant for fall: Jul 15 to Jul 29
Sow outdoors: Apr 13 to May 11Plant for fall: Jul 29 to Aug 12
Sow outdoors: Apr 13 to May 4
Sow outdoors: Apr 20 to May 18Plant for fall: Jul 29 to Aug 12
Sow outdoors: Apr 20 to May 11Plant for fall: Aug 12 to Sep 2
Sow outdoors: May 11 to Jun 1Plant for fall: Jul 22 to Aug 5
Sow outdoors: May 11 to May 25
Transplant outside: May 18 to Jun 8
Plant for fall: Sep 23 to Oct 28
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Acton, MT
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Feb 9 – Feb 23 | Apr 6 – Apr 20 | — | — |
| Peppers | Feb 23 – Mar 9 | May 18 – Jun 1 | — | — |
| Eggplant | Feb 23 – Mar 9 | May 18 – Jun 1 | — | — |
| Tomatoes | Mar 9 – Mar 23 | May 11 – May 25 | — | — |
| Lettuce | Mar 9 – Mar 23 | Apr 13 – Apr 27 | Apr 6 – May 11 | Aug 12 – Sep 9 |
| Kale | Mar 9 – Mar 23 | Apr 6 – Apr 20 | Apr 6 – Apr 20 | Jul 29 – Aug 19 |
| Broccoli | Mar 9 – Mar 23 | Apr 20 – May 4 | — | Jul 1 – Jul 22 |
| Cabbage | Mar 9 – Mar 23 | Apr 13 – Apr 27 | — | Jul 1 – Jul 22 |
| Cauliflower | Mar 9 – Mar 23 | Apr 20 – May 4 | — | Jul 1 – Jul 22 |
| Okra | Mar 23 – Apr 6 | May 25 – Jun 8 | May 25 – Jun 8 | — |
| Basil | Mar 23 – Apr 6 | May 11 – May 25 | — | — |
| Peas | — | — | Mar 23 – Apr 13 | Jul 15 – Aug 5 |
| Spinach | — | — | Mar 23 – Apr 13 | Aug 12 – Sep 2 |
| Radishes | — | — | Mar 30 – May 11 | Aug 26 – Sep 16 |
| Cucumbers | Apr 6 – Apr 13 | May 18 – May 25 | May 11 – May 25 | Jul 22 – Aug 5 |
| Zucchini & Summer Squash | Apr 6 – Apr 13 | — | May 11 – May 25 | Jul 29 – Aug 12 |
| Winter Squash & Pumpkins | Apr 6 – Apr 13 | — | May 11 – May 25 | — |
| Melons & Watermelon | Apr 6 – Apr 13 | May 18 – Jun 1 | — | — |
| Carrots | — | — | Apr 13 – May 11 | Jul 15 – Jul 29 |
| Beets | — | — | Apr 13 – May 11 | Jul 29 – Aug 12 |
| Potatoes | — | — | Apr 13 – May 4 | — |
| Swiss Chard | — | — | Apr 20 – May 18 | Jul 29 – Aug 12 |
| Cilantro | — | — | Apr 20 – May 11 | Aug 12 – Sep 2 |
| Green Beans | — | — | May 11 – Jun 1 | Jul 22 – Aug 5 |
| Sweet Corn | — | — | May 11 – May 25 | — |
| Sweet Potatoes | — | May 18 – Jun 8 | — | — |
| Garlic | — | — | — | Sep 23 – Oct 28 |
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 Billings Logan Intl Ap, MT weather station, 18 km away (elevation 3,583 ft (1,092 m)).
Frost dates near Acton
- Broadview May 22 · Sep 15
- Billings May 4 · Oct 7
- Molt May 24 · Sep 21
- Shepherd May 12 · Sep 25
- Laurel May 5 · Oct 3
- Huntley May 12 · Sep 25
- Park City May 29 · Sep 15
- Worden May 12 · Sep 25
- Ballantine May 12 · Sep 25
- Rapelje May 24 · Sep 21
Frequently asked questions
When is the last frost in Acton, MT?
The median last spring frost in Acton, MT is May 4. There is still about a 10% chance of frost after May 18, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Acton, MT?
The median first fall frost is October 7, with about a 10% chance of frost before September 26.
How long is the growing season in Acton, MT?
About 156 days between the median last spring frost and first fall frost.
What planting zone is Acton, MT?
Acton, MT is in USDA hardiness zone 5a.