Frost dates for 56731Humboldt, MN
The average last spring frost in Humboldt is May 16 and the average first fall frost is September 29, giving a typical growing season of about 137 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 16
- Average first fall frost
- Sep 29
- Growing season
- 137 days
Safer after May 31 (1-in-10 risk)
Possible by Sep 17 (1-in-10 risk)
Last frost typically in 201 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 11 · May 25 · Jun 7 | Sep 7 · Sep 20 · Oct 2 | 116 days | 100% |
| Frost / freeze (32°F) | May 2 · May 16 · May 31 | Sep 17 · Sep 29 · Oct 11 | 137 days | 100% |
| Hard freeze (28°F) | Apr 20 · May 5 · May 21 | Sep 26 · Oct 7 · Oct 21 | 155 days | 100% |
Planting calendar for Humboldt
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 15 – Jun 21 |
| Tomatoes | Transplant outdoors | Jun 1 – Jun 9 |
| Peppers | Start seeds indoors | Apr 15 – May 16 |
| Peppers | Transplant outdoors | Jun 15 – Jul 16 |
| Eggplant | Start seeds indoors | May 2 – May 31 |
| Eggplant | Transplant outdoors | Jun 15 – Jul 16 |
| Cucumbers | Sow outdoors | Jun 15 – Jun 19 |
| Summer squash | Sow outdoors | Jun 1 – Jul 16 |
| Winter squash & pumpkins | Sow outdoors | Jun 15 – Jul 16 |
| Snap beans | Sow outdoors | Jun 1 – Jul 12 |
| Sweet corn | Sow outdoors | Jun 1 – Jun 9 |
| Watermelon & cantaloupe | Sow outdoors | Jun 15 – Jul 16 |
| Okra | Sow outdoors | Jun 8 – Jul 1 |
| Peas | Sow outdoors (spring) | Apr 15 – May 31 |
| Potatoes | Plant outdoors (spring) | Apr 15 – Jun 15 |
| Onions | Start seeds indoors (spring) | Mar 4 – Mar 31 |
| Onions | Transplant outdoors (spring) | May 2 – May 31 |
| Broccoli | Start seeds indoors (spring) | Mar 28 – May 1 |
| Broccoli | Transplant outdoors (spring) | May 2 – May 31 |
| Broccoli | Start seeds indoors (fall) | May 30 – Jun 9 |
| Broccoli | Transplant outdoors (fall) | Jun 29 – Jul 10 |
| Cabbage | Start seeds indoors (spring) | Mar 18 – Apr 15 |
| Cabbage | Transplant outdoors (spring) | Apr 15 – May 16 |
| Cabbage | Start seeds indoors (fall) | May 20 – Jun 19 |
| Cabbage | Transplant outdoors (fall) | Jun 19 – Jul 20 |
| Leaf lettuce | Sow outdoors (spring) | Apr 15 – Jul 1 |
| Leaf lettuce | Sow outdoors (fall) | Jun 19 – Aug 5 |
| Spinach | Sow outdoors (spring) | Apr 8 – May 22 |
| Spinach | Sow outdoors (fall) | Jul 6 – Aug 10 |
| Radishes | Sow outdoors (spring) | Apr 15 – Jun 5 |
| Radishes | Sow outdoors (fall) | Jun 19 – Aug 20 |
| Kale | Sow outdoors (spring) | May 2 – May 22 |
| Kale | Sow outdoors (fall) | Jun 12 – Jul 20 |
| Carrots | Sow outdoors (spring) | May 16 – Jul 1 |
| Carrots | Sow outdoors (fall) | May 20 – Jul 5 |
| Garlic | Plant outdoors (fall) | Sep 19 – Oct 20 |
Where these dates come from
ZIP code 56731 is matched to the NOAA station Pembina, ND, 12.2 km away, at 790 ft elevation (7 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Pembina, ND (used) | 790 ft | May 16 | Sep 29 |
| Hallock, MN | 815 ft | May 8 | Sep 30 |
| Cavalier 7Nw, ND | 899 ft | May 12 | Sep 30 |
| Grafton, ND | 827 ft | May 4 | Oct 7 |
Frost dates near Humboldt
- Saint Vincent, MN 56755 · last May 16, first Sep 29
- Noyes, MN 56740 · last May 16, first Sep 29
- Pembina, ND 58271 · last May 16, first Sep 29
- Hallock, MN 56728 · last May 8, first Sep 30
- Bathgate, ND 58216 · last May 12, first Sep 30
- Hamilton, ND 58238 · last May 12, first Sep 30
- Lancaster, MN 56735 · last May 8, first Sep 30
- Kennedy, MN 56733 · last May 8, first Sep 30
Frequently asked questions
- When is the last frost in Humboldt, MN?
- For ZIP code 56731, the average last spring frost (32°F) is May 16, based on NOAA 1991-2020 climate normals for the Pembina, ND weather station. There is a 1-in-10 chance of a frost after May 31.
- When is the first frost in Humboldt, MN?
- The average first fall frost (32°F) is September 29. There is a 1-in-10 chance of frost by September 17, so tender plants are at risk from that point on.
- How long is the growing season in 56731?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 137 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.