Frost dates for 55607Isabella, MN
The average last spring frost in Isabella is May 31 and the average first fall frost is September 15, giving a typical growing season of about 104 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 31
- Average first fall frost
- Sep 15
- Growing season
- 104 days
Safer after Jun 21 (1-in-10 risk)
Possible by Aug 30 (1-in-10 risk)
Last frost typically in 216 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) | — | — | 75 days | 100% |
| Frost / freeze (32°F) | May 16 · May 31 · Jun 21 | Aug 30 · Sep 15 · Sep 29 | 104 days | 100% |
| Hard freeze (28°F) | May 2 · May 16 · May 31 | Sep 8 · Sep 25 · Oct 10 | 129 days | 100% |
Planting calendar for Isabella
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 30 – Jul 6 |
| Tomatoes | Transplant outdoors | Jun 16 – May 26 |
| Peppers | Start seeds indoors | Apr 30 – May 31 |
| Peppers | Transplant outdoors | Jun 30 – Jul 31 |
| Eggplant | Start seeds indoors | May 17 – Jun 15 |
| Eggplant | Transplant outdoors | Jun 30 – Jul 31 |
| Cucumbers | Sow outdoors | Jun 30 – Jun 5 |
| Summer squash | Sow outdoors | Jun 16 – Jul 31 |
| Winter squash & pumpkins | Sow outdoors | Jun 30 – Jul 31 |
| Snap beans | Sow outdoors | Jun 16 – Jun 28 |
| Sweet corn | Sow outdoors | Jun 16 – May 26 |
| Watermelon & cantaloupe | Sow outdoors | Jun 30 – Jul 31 |
| Okra | Sow outdoors | Jun 23 – Jul 16 |
| Peas | Sow outdoors (spring) | Apr 30 – Jun 15 |
| Potatoes | Plant outdoors (spring) | Apr 30 – Jun 30 |
| Onions | Start seeds indoors (spring) | Mar 19 – Apr 15 |
| Onions | Transplant outdoors (spring) | May 17 – Jun 15 |
| Broccoli | Start seeds indoors (spring) | Apr 12 – May 16 |
| Broccoli | Transplant outdoors (spring) | May 17 – Jun 15 |
| Broccoli | Start seeds indoors (fall) | May 16 – May 26 |
| Broccoli | Transplant outdoors (fall) | Jun 15 – Jun 26 |
| Cabbage | Start seeds indoors (spring) | Apr 2 – Apr 30 |
| Cabbage | Transplant outdoors (spring) | Apr 30 – May 31 |
| Cabbage | Start seeds indoors (fall) | May 6 – Jun 5 |
| Cabbage | Transplant outdoors (fall) | Jun 5 – Jul 6 |
| Leaf lettuce | Sow outdoors (spring) | Apr 30 – Jul 16 |
| Leaf lettuce | Sow outdoors (fall) | Jun 5 – Jul 22 |
| Spinach | Sow outdoors (spring) | Apr 23 – Jun 6 |
| Spinach | Sow outdoors (fall) | Jun 22 – Jul 27 |
| Radishes | Sow outdoors (spring) | Apr 30 – Jun 20 |
| Radishes | Sow outdoors (fall) | Jun 5 – Aug 6 |
| Kale | Sow outdoors (spring) | May 17 – Jun 6 |
| Kale | Sow outdoors (fall) | May 29 – Jul 6 |
| Carrots | Sow outdoors (spring) | May 31 – Jul 16 |
| Carrots | Sow outdoors (fall) | May 6 – Jun 21 |
| Garlic | Plant outdoors (fall) | Sep 5 – Oct 6 |
Where these dates come from
ZIP code 55607 is matched to the NOAA station Isabella 14W, MN, 13.6 km away, at 1,740 ft elevation (38 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Isabella 14W, MN (used) | 1,740 ft | May 31 | Sep 15 |
| Wolf Ridge Elc, MN | 1,400 ft | May 15 | Oct 1 |
| Babbitt, MN | 1,481 ft | May 28 | Sep 14 |
| Ely 25E, MN | 1,444 ft | May 21 | Sep 25 |
Frost dates near Isabella
- Finland, MN 55603 · last May 15, first Oct 1
- Babbitt, MN 55706 · last May 28, first Sep 14
- Winton, MN 55796 · last May 24, first Sep 23
- Ely, MN 55731 · last May 14, first Sep 29
- Silver Bay, MN 55614 · last May 15, first Oct 1
- Schroeder, MN 55613 · last May 26, first Sep 27
- Beaver Bay, MN 55601 · last May 15, first Oct 1
- Brimson, MN 55602 · last —, first —
Frequently asked questions
- When is the last frost in Isabella, MN?
- For ZIP code 55607, the average last spring frost (32°F) is May 31, based on NOAA 1991-2020 climate normals for the Isabella 14W, MN weather station. There is a 1-in-10 chance of a frost after June 21.
- When is the first frost in Isabella, MN?
- The average first fall frost (32°F) is September 15. There is a 1-in-10 chance of frost by August 30, so tender plants are at risk from that point on.
- How long is the growing season in 55607?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 104 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.