Frost dates for 56701Thief River Falls, MN
The average last spring frost in Thief River Falls is May 14 and the average first fall frost is September 28, giving a typical growing season of about 135 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 14
- Average first fall frost
- Sep 28
- Growing season
- 135 days
Safer after May 29 (1-in-10 risk)
Possible by Sep 14 (1-in-10 risk)
Last frost typically in 192 days
Frost risk by date
NOAA reports frost dates as probabilities. The middle date is the average (a 50% chance). For spring, the 10% date is a safer planting date: frost after it happens in about 1 year in 10. Light frost (36°F) can damage tender plants; a hard freeze (28°F) kills most annuals.
| Temperature | Last spring: 90% / 50% / 10% chance | First fall: 10% / 50% / 90% chance | Growing season (50%) | Years with at least one |
|---|---|---|---|---|
| Light frost (36°F) | May 12 · May 24 · Jun 7 | Sep 3 · Sep 18 · Sep 30 | 113 days | 100% |
| Frost / freeze (32°F) | May 2 · May 14 · May 29 | Sep 14 · Sep 28 · Oct 11 | 135 days | 100% |
| Hard freeze (28°F) | Apr 21 · May 5 · May 20 | Sep 24 · Oct 8 · Oct 25 | 155 days | 100% |
Planting calendar for Thief River Falls
Planting windows from the University of Maryland Extension calendar, shifted to your average frost dates. Use them as a starting point and adjust for seed packet instructions and local conditions.
| Crop | Task | Window |
|---|---|---|
| Tomatoes | Start seeds indoors | Apr 13 – Jun 19 |
| Tomatoes | Transplant outdoors | May 30 – Jun 8 |
| Peppers | Start seeds indoors | Apr 13 – May 14 |
| Peppers | Transplant outdoors | Jun 13 – Jul 14 |
| Eggplant | Start seeds indoors | Apr 30 – May 29 |
| Eggplant | Transplant outdoors | Jun 13 – Jul 14 |
| Cucumbers | Sow outdoors | Jun 13 – Jun 18 |
| Summer squash | Sow outdoors | May 30 – Jul 14 |
| Winter squash & pumpkins | Sow outdoors | Jun 13 – Jul 14 |
| Snap beans | Sow outdoors | May 30 – Jul 11 |
| Sweet corn | Sow outdoors | May 30 – Jun 8 |
| Watermelon & cantaloupe | Sow outdoors | Jun 13 – Jul 14 |
| Okra | Sow outdoors | Jun 6 – Jun 29 |
| Peas | Sow outdoors (spring) | Apr 13 – May 29 |
| Potatoes | Plant outdoors (spring) | Apr 13 – Jun 13 |
| Onions | Start seeds indoors (spring) | Mar 2 – Mar 29 |
| Onions | Transplant outdoors (spring) | Apr 30 – May 29 |
| Broccoli | Start seeds indoors (spring) | Mar 26 – Apr 29 |
| Broccoli | Transplant outdoors (spring) | Apr 30 – May 29 |
| Broccoli | Start seeds indoors (fall) | May 29 – Jun 8 |
| Broccoli | Transplant outdoors (fall) | Jun 28 – Jul 9 |
| Cabbage | Start seeds indoors (spring) | Mar 16 – Apr 13 |
| Cabbage | Transplant outdoors (spring) | Apr 13 – May 14 |
| Cabbage | Start seeds indoors (fall) | May 19 – Jun 18 |
| Cabbage | Transplant outdoors (fall) | Jun 18 – Jul 19 |
| Leaf lettuce | Sow outdoors (spring) | Apr 13 – Jun 29 |
| Leaf lettuce | Sow outdoors (fall) | Jun 18 – Aug 4 |
| Spinach | Sow outdoors (spring) | Apr 6 – May 20 |
| Spinach | Sow outdoors (fall) | Jul 5 – Aug 9 |
| Radishes | Sow outdoors (spring) | Apr 13 – Jun 3 |
| Radishes | Sow outdoors (fall) | Jun 18 – Aug 19 |
| Kale | Sow outdoors (spring) | Apr 30 – May 20 |
| Kale | Sow outdoors (fall) | Jun 11 – Jul 19 |
| Carrots | Sow outdoors (spring) | May 14 – Jun 29 |
| Carrots | Sow outdoors (fall) | May 19 – Jul 4 |
| Garlic | Plant outdoors (fall) | Sep 18 – Oct 19 |
Where these dates come from
ZIP code 56701 is matched to the NOAA station Thief Rvr Falls 2, MN, 1.5 km away, at 1,128 ft elevation (7 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Thief Rvr Falls 2, MN (used) | 1,128 ft | May 14 | Sep 28 |
| Agassiz Refuge, MN | 1,142 ft | May 6 | Oct 3 |
| Red Lake Falls, MN | 1,038 ft | May 9 | Sep 30 |
| Goodridge 12 Nnw, MN | 1,150 ft | May 20 | Sep 17 |
Frost dates near Thief River Falls
- Saint Hilaire, MN 56754 · last May 14, first Sep 28
- Newfolden, MN 56738 · last May 14, first Sep 28
- Viking, MN 56760 · last May 14, first Sep 28
- Red Lake Falls, MN 56750 · last May 9, first Sep 30
- Plummer, MN 56748 · last May 9, first Sep 30
- Goodridge, MN 56725 · last May 20, first Sep 17
- Middle River, MN 56737 · last May 20, first Sep 17
- Brooks, MN 56715 · last May 9, first Sep 30
Frequently asked questions
- When is the last frost in Thief River Falls, MN?
- For ZIP code 56701, the average last spring frost (32°F) is May 14, based on NOAA 1991-2020 climate normals for the Thief Rvr Falls 2, MN weather station. There is a 1-in-10 chance of a frost after May 29.
- When is the first frost in Thief River Falls, MN?
- The average first fall frost (32°F) is September 28. There is a 1-in-10 chance of frost by September 14, so tender plants are at risk from that point on.
- How long is the growing season in 56701?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 135 days long.
- Are these frost dates a forecast?
- No. They are 30-year averages and probabilities from NOAA weather station records. Use them to plan, then watch your local forecast before planting tender crops or leaving them uncovered.