Frost dates for 55816Duluth, MN
The average last spring frost in Duluth is May 6 and the average first fall frost is October 9, giving a typical growing season of about 154 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 6
- Average first fall frost
- Oct 9
- Growing season
- 154 days
Safer after May 25 (1-in-10 risk)
Possible by Sep 24 (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 6 · May 21 · Jun 8 | Sep 15 · Sep 28 · Oct 11 | 130 days | 100% |
| Frost / freeze (32°F) | Apr 24 · May 6 · May 25 | Sep 24 · Oct 9 · Oct 24 | 154 days | 100% |
| Hard freeze (28°F) | Apr 10 · Apr 24 · May 9 | Oct 6 · Oct 24 · Nov 7 | 181 days | 100% |
Planting calendar for Duluth
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 5 – Jun 11 |
| Tomatoes | Transplant outdoors | May 22 – Jun 19 |
| Peppers | Start seeds indoors | Apr 5 – May 6 |
| Peppers | Transplant outdoors | Jun 5 – Jul 6 |
| Eggplant | Start seeds indoors | Apr 22 – May 21 |
| Eggplant | Transplant outdoors | Jun 5 – Jul 6 |
| Cucumbers | Sow outdoors | Jun 5 – Jun 29 |
| Summer squash | Sow outdoors | May 22 – Jul 6 |
| Winter squash & pumpkins | Sow outdoors | Jun 5 – Jul 6 |
| Snap beans | Sow outdoors | May 22 – Jul 22 |
| Sweet corn | Sow outdoors | May 22 – Jun 19 |
| Watermelon & cantaloupe | Sow outdoors | Jun 5 – Jul 6 |
| Okra | Sow outdoors | May 29 – Jun 21 |
| Peas | Sow outdoors (spring) | Apr 5 – May 21 |
| Potatoes | Plant outdoors (spring) | Apr 5 – Jun 5 |
| Onions | Start seeds indoors (spring) | Feb 22 – Mar 21 |
| Onions | Transplant outdoors (spring) | Apr 22 – May 21 |
| Broccoli | Start seeds indoors (spring) | Mar 18 – Apr 21 |
| Broccoli | Transplant outdoors (spring) | Apr 22 – May 21 |
| Broccoli | Start seeds indoors (fall) | Jun 9 – Jun 19 |
| Broccoli | Transplant outdoors (fall) | Jul 9 – Jul 20 |
| Cabbage | Start seeds indoors (spring) | Mar 8 – Apr 5 |
| Cabbage | Transplant outdoors (spring) | Apr 5 – May 6 |
| Cabbage | Start seeds indoors (fall) | May 30 – Jun 29 |
| Cabbage | Transplant outdoors (fall) | Jun 29 – Jul 30 |
| Leaf lettuce | Sow outdoors (spring) | Apr 5 – Jun 21 |
| Leaf lettuce | Sow outdoors (fall) | Jun 29 – Aug 15 |
| Spinach | Sow outdoors (spring) | Mar 29 – May 12 |
| Spinach | Sow outdoors (fall) | Jul 16 – Aug 20 |
| Radishes | Sow outdoors (spring) | Apr 5 – May 26 |
| Radishes | Sow outdoors (fall) | Jun 29 – Aug 30 |
| Kale | Sow outdoors (spring) | Apr 22 – May 12 |
| Kale | Sow outdoors (fall) | Jun 22 – Jul 30 |
| Carrots | Sow outdoors (spring) | May 6 – Jun 21 |
| Carrots | Sow outdoors (fall) | May 30 – Jul 15 |
| Garlic | Plant outdoors (fall) | Sep 29 – Oct 30 |
Where these dates come from
ZIP code 55816 is matched to the NOAA station Superior, WI, 6.8 km away, at 607 ft elevation (95 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Superior, WI (used) | 607 ft | May 6 | Oct 9 |
| Duluth Harbor Stn, MN | 610 ft | May 14 | Oct 12 |
| Duluth, MN | 1,428 ft | May 13 | Oct 1 |
| Duluth Nws, MN | 1,433 ft | May 18 | Oct 1 |
Frost dates near Duluth
- Duluth, MN 55801 · last May 6, first Oct 9
- Superior, WI 54880 · last May 6, first Oct 9
- Esko, MN 55733 · last May 26, first Sep 23
- Twig, MN 55791 · last May 13, first Oct 1
- Saginaw, MN 55779 · last May 13, first Oct 1
- South Range, WI 54874 · last May 18, first Oct 3
- Wrenshall, MN 55797 · last Jun 1, first Sep 22
- Knife River, MN 55609 · last May 12, first Oct 6
Frequently asked questions
- When is the last frost in Duluth, MN?
- For ZIP code 55816, the average last spring frost (32°F) is May 6, based on NOAA 1991-2020 climate normals for the Superior, WI weather station. There is a 1-in-10 chance of a frost after May 25.
- When is the first frost in Duluth, MN?
- The average first fall frost (32°F) is October 9. There is a 1-in-10 chance of frost by September 24, so tender plants are at risk from that point on.
- How long is the growing season in 55816?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 154 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.