Frost dates for 55605Grand Portage, MN
The average last spring frost in Grand Portage is May 24 and the average first fall frost is September 29, giving a typical growing season of about 127 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 24
- Average first fall frost
- Sep 29
- Growing season
- 127 days
Safer after Jun 5 (1-in-10 risk)
Possible by Sep 16 (1-in-10 risk)
Last frost typically in 209 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 23 · Jun 3 · Jun 16 | Sep 3 · Sep 18 · Oct 1 | 105 days | 100% |
| Frost / freeze (32°F) | May 7 · May 24 · Jun 5 | Sep 16 · Sep 29 · Oct 10 | 127 days | 100% |
| Hard freeze (28°F) | Apr 27 · May 9 · May 25 | Sep 25 · Oct 9 · Oct 27 | 153 days | 100% |
Planting calendar for Grand Portage
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 23 – Jun 29 |
| Tomatoes | Transplant outdoors | Jun 9 – Jun 9 |
| Peppers | Start seeds indoors | Apr 23 – May 24 |
| Peppers | Transplant outdoors | Jun 23 – Jul 24 |
| Eggplant | Start seeds indoors | May 10 – Jun 8 |
| Eggplant | Transplant outdoors | Jun 23 – Jul 24 |
| Cucumbers | Sow outdoors | Jun 23 – Jun 19 |
| Summer squash | Sow outdoors | Jun 9 – Jul 24 |
| Winter squash & pumpkins | Sow outdoors | Jun 23 – Jul 24 |
| Snap beans | Sow outdoors | Jun 9 – Jul 12 |
| Sweet corn | Sow outdoors | Jun 9 – Jun 9 |
| Watermelon & cantaloupe | Sow outdoors | Jun 23 – Jul 24 |
| Okra | Sow outdoors | Jun 16 – Jul 9 |
| Peas | Sow outdoors (spring) | Apr 23 – Jun 8 |
| Potatoes | Plant outdoors (spring) | Apr 23 – Jun 23 |
| Onions | Start seeds indoors (spring) | Mar 12 – Apr 8 |
| Onions | Transplant outdoors (spring) | May 10 – Jun 8 |
| Broccoli | Start seeds indoors (spring) | Apr 5 – May 9 |
| Broccoli | Transplant outdoors (spring) | May 10 – Jun 8 |
| Broccoli | Start seeds indoors (fall) | May 30 – Jun 9 |
| Broccoli | Transplant outdoors (fall) | Jun 29 – Jul 10 |
| Cabbage | Start seeds indoors (spring) | Mar 26 – Apr 23 |
| Cabbage | Transplant outdoors (spring) | Apr 23 – May 24 |
| Cabbage | Start seeds indoors (fall) | May 20 – Jun 19 |
| Cabbage | Transplant outdoors (fall) | Jun 19 – Jul 20 |
| Leaf lettuce | Sow outdoors (spring) | Apr 23 – Jul 9 |
| Leaf lettuce | Sow outdoors (fall) | Jun 19 – Aug 5 |
| Spinach | Sow outdoors (spring) | Apr 16 – May 30 |
| Spinach | Sow outdoors (fall) | Jul 6 – Aug 10 |
| Radishes | Sow outdoors (spring) | Apr 23 – Jun 13 |
| Radishes | Sow outdoors (fall) | Jun 19 – Aug 20 |
| Kale | Sow outdoors (spring) | May 10 – May 30 |
| Kale | Sow outdoors (fall) | Jun 12 – Jul 20 |
| Carrots | Sow outdoors (spring) | May 24 – Jul 9 |
| Carrots | Sow outdoors (fall) | May 20 – Jul 5 |
| Garlic | Plant outdoors (fall) | Sep 19 – Oct 20 |
Where these dates come from
ZIP code 55605 is matched to the NOAA station Grand Portage, MN, 1.5 km away, at 730 ft elevation (25 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Grand Portage, MN (used) | 730 ft | May 24 | Sep 29 |
| Grand Marais, MN | 612 ft | May 20 | Oct 5 |
| Grand Marais, MN | 610 ft | May 22 | Oct 9 |
| Lutsen 3Nne, MN | 1,300 ft | May 26 | Sep 27 |
Frost dates near Grand Portage
- Hovland, MN 55606 · last May 20, first Oct 5
- Grand Marais, MN 55604 · last May 26, first Sep 27
- Lutsen, MN 55612 · last May 26, first Sep 27
- Tofte, MN 55615 · last May 22, first Oct 9
- Schroeder, MN 55613 · last May 26, first Sep 27
- Allouez, MI 49805 · last May 17, first Oct 1
- Calumet, MI 49913 · last May 17, first Oct 1
- Kearsarge, MI 49942 · last May 17, first Oct 1
Frequently asked questions
- When is the last frost in Grand Portage, MN?
- For ZIP code 55605, the average last spring frost (32°F) is May 24, based on NOAA 1991-2020 climate normals for the Grand Portage, MN weather station. There is a 1-in-10 chance of a frost after June 5.
- When is the first frost in Grand Portage, MN?
- The average first fall frost (32°F) is September 29. There is a 1-in-10 chance of frost by September 16, so tender plants are at risk from that point on.
- How long is the growing season in 55605?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 127 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.