Chinook, MT frost dates
Last spring frostMay 14median date
First fall frostSep 23median date
Growing season132 daysfrost-free
Hardiness zone3bZone 3b
How Chinook compares
- In 8 years out of 10, the last spring frost in Chinook falls between May 1 and May 27, a 26-day window. The first fall frost falls between September 11 and October 3.
- The median last frost is 5 days earlier than the Montana median of May 19.
- Its 132-day growing season is longer than 64% of the 325 Montana places with a regular frost season (state median 125 days).
- The last frost is typical for zone 3b, where the median is May 17.
- The weather station records an average of 195 nights a year at or below 32°F.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | May 1 |
| 50% (median) | May 14 |
| 10% (safe for tender plants) | May 27 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | September 11 |
| 50% (median) | September 23 |
| 90% (late) | October 3 |
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 Chinook, MT
Chinook, MT frost dates — last frost May 14, first frost Sep 23, zone 3b. 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: Jul 29 to Aug 26
Start indoors: Mar 19 to Apr 2Transplant outside: Apr 16 to Apr 30Sow outdoors: Apr 16 to Apr 30Plant for fall: Jul 15 to Aug 5
Start indoors: Mar 19 to Apr 2Transplant outside: Apr 30 to May 14Plant for fall: Jun 17 to Jul 8
Start indoors: Mar 19 to Apr 2Transplant outside: Apr 23 to May 7Plant for fall: Jun 17 to Jul 8
Start indoors: Mar 19 to Apr 2Transplant outside: Apr 30 to May 14Plant for fall: Jun 17 to Jul 8
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 1 to Jul 22
Sow outdoors: Apr 2 to Apr 23Plant for fall: Jul 29 to Aug 19
Sow outdoors: Apr 9 to May 21Plant for fall: Aug 12 to Sep 2
Start indoors: Apr 16 to Apr 23Transplant outside: May 28 to Jun 4Sow outdoors: May 21 to Jun 4Plant for fall: Jul 8 to Jul 22
Start indoors: Apr 16 to Apr 23Sow outdoors: May 21 to Jun 4Plant for fall: Jul 15 to Jul 29
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 1 to Jul 15
Sow outdoors: Apr 23 to May 21Plant for fall: Jul 15 to Jul 29
Sow outdoors: Apr 23 to May 14
Sow outdoors: Apr 30 to May 28Plant for fall: Jul 15 to Jul 29
Sow outdoors: Apr 30 to May 21Plant for fall: Jul 29 to Aug 19
Sow outdoors: May 21 to Jun 11Plant for fall: Jul 8 to Jul 22
Sow outdoors: May 21 to Jun 4
Transplant outside: May 28 to Jun 18
Plant for fall: Sep 9 to Oct 14
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Chinook, 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 | Jul 29 – Aug 26 |
| Kale | Mar 19 – Apr 2 | Apr 16 – Apr 30 | Apr 16 – Apr 30 | Jul 15 – Aug 5 |
| Broccoli | Mar 19 – Apr 2 | Apr 30 – May 14 | — | Jun 17 – Jul 8 |
| Cabbage | Mar 19 – Apr 2 | Apr 23 – May 7 | — | Jun 17 – Jul 8 |
| Cauliflower | Mar 19 – Apr 2 | Apr 30 – May 14 | — | Jun 17 – Jul 8 |
| 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 1 – Jul 22 |
| Spinach | — | — | Apr 2 – Apr 23 | Jul 29 – Aug 19 |
| Radishes | — | — | Apr 9 – May 21 | Aug 12 – Sep 2 |
| Cucumbers | Apr 16 – Apr 23 | May 28 – Jun 4 | May 21 – Jun 4 | Jul 8 – Jul 22 |
| Zucchini & Summer Squash | Apr 16 – Apr 23 | — | May 21 – Jun 4 | Jul 15 – Jul 29 |
| 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 1 – Jul 15 |
| Beets | — | — | Apr 23 – May 21 | Jul 15 – Jul 29 |
| Potatoes | — | — | Apr 23 – May 14 | — |
| Swiss Chard | — | — | Apr 30 – May 28 | Jul 15 – Jul 29 |
| Cilantro | — | — | Apr 30 – May 21 | Jul 29 – Aug 19 |
| Green Beans | — | — | May 21 – Jun 11 | Jul 8 – Jul 22 |
| Sweet Corn | — | — | May 21 – Jun 4 | — |
| Sweet Potatoes | — | May 28 – Jun 18 | — | — |
| Garlic | — | — | — | Sep 9 – Oct 14 |
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 Chinook, MT weather station, about 1 km away (elevation 2,421 ft (738 m)).
Frost dates near Chinook
- Zurich May 14 · Sep 23
- Harlem May 16 · Sep 21
- Havre May 15 · Sep 23
- Hogeland May 19 · Sep 21
- Box Elder May 15 · Sep 24
- Kremlin May 24 · Sep 15
- Turner May 19 · Sep 21
- Lloyd May 23 · Sep 23
- Dodson May 10 · Sep 29
- Hays May 18 · Sep 23
Frequently asked questions
When is the last frost in Chinook, MT?
The median last spring frost in Chinook, 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 Chinook, MT?
The median first fall frost is September 23, with about a 10% chance of frost before September 11.
How long is the growing season in Chinook, MT?
About 132 days between the median last spring frost and first fall frost.
What planting zone is Chinook, MT?
Chinook, MT is in USDA hardiness zone 3b.