Thief River Falls, MN frost dates
Last spring frostMay 14median date
First fall frostSep 28median date
Growing season137 daysfrost-free
Hardiness zone4aZone 4a
How Thief River Falls compares
- In 8 years out of 10, the last spring frost in Thief River Falls falls between May 2 and May 29, a 27-day window. The first fall frost falls between September 14 and October 11.
- The median last frost is 9 days later than the Minnesota median of May 5.
- Its 137-day growing season is longer than 16% of the 801 Minnesota places with a regular frost season (state median 151 days).
- The last frost is typical for zone 4a, where the median is May 12.
- The weather station records an average of 182 nights a year at or below 32°F.
- Compared with Grand Forks, ND, 68 km away, the last frost here is 4 days later than there and the growing season is 7 days shorter.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | May 2 |
| 50% (median) | May 14 |
| 10% (safe for tender plants) | May 29 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | September 14 |
| 50% (median) | September 28 |
| 90% (late) | October 11 |
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 Thief River Falls, MN
Thief River Falls, MN frost dates — last frost May 14, first frost Sep 28, zone 4a. 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 Thief River Falls, MN
| 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 Thief Rvr Falls, MN weather station, 2 km away (elevation 1,129 ft (344 m)).
Frost dates near Thief River Falls
- Saint Hilaire May 14 · Sep 28
- Newfolden May 14 · Sep 28
- Viking May 5 · Oct 2
- Red Lake Falls May 9 · Sep 30
- Plummer May 9 · Sep 30
- Goodridge May 20 · Sep 17
- Brooks May 9 · Sep 30
- Middle River May 6 · Oct 3
- Euclid May 11 · Sep 27
- Oklee May 15 · Sep 26
Frequently asked questions
When is the last frost in Thief River Falls, MN?
The median last spring frost in Thief River Falls, MN is May 14. There is still about a 10% chance of frost after May 29, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Thief River Falls, MN?
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 Thief River Falls, MN?
About 137 days between the median last spring frost and first fall frost.
What planting zone is Thief River Falls, MN?
Thief River Falls, MN is in USDA hardiness zone 4a.