Frost dates for 48721Black River, MI
The average last spring frost in Black River is May 8 and the average first fall frost is October 16, giving a typical growing season of about 160 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 8
- Average first fall frost
- Oct 16
- Growing season
- 160 days
Safer after May 24 (1-in-10 risk)
Possible by Oct 2 (1-in-10 risk)
Last frost typically in 187 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 4 | Sep 23 · Oct 4 · Oct 17 | 135 days | 100% |
| Frost / freeze (32°F) | Apr 26 · May 8 · May 24 | Oct 2 · Oct 16 · Oct 30 | 160 days | 100% |
| Hard freeze (28°F) | Apr 13 · Apr 27 · May 12 | Oct 15 · Oct 29 · Nov 12 | 183 days | 100% |
Planting calendar for Black River
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 7 – Jun 13 |
| Tomatoes | Transplant outdoors | May 24 – Jun 26 |
| Peppers | Start seeds indoors | Apr 7 – May 8 |
| Peppers | Transplant outdoors | Jun 7 – Jul 8 |
| Eggplant | Start seeds indoors | Apr 24 – May 23 |
| Eggplant | Transplant outdoors | Jun 7 – Jul 8 |
| Cucumbers | Sow outdoors | Jun 7 – Jul 6 |
| Summer squash | Sow outdoors | May 24 – Jul 8 |
| Winter squash & pumpkins | Sow outdoors | Jun 7 – Jul 8 |
| Snap beans | Sow outdoors | May 24 – Jul 29 |
| Sweet corn | Sow outdoors | May 24 – Jun 26 |
| Watermelon & cantaloupe | Sow outdoors | Jun 7 – Jul 8 |
| Okra | Sow outdoors | May 31 – Jun 23 |
| Peas | Sow outdoors (spring) | Apr 7 – May 23 |
| Potatoes | Plant outdoors (spring) | Apr 7 – Jun 7 |
| Onions | Start seeds indoors (spring) | Feb 24 – Mar 23 |
| Onions | Transplant outdoors (spring) | Apr 24 – May 23 |
| Broccoli | Start seeds indoors (spring) | Mar 20 – Apr 23 |
| Broccoli | Transplant outdoors (spring) | Apr 24 – May 23 |
| Broccoli | Start seeds indoors (fall) | Jun 16 – Jun 26 |
| Broccoli | Transplant outdoors (fall) | Jul 16 – Jul 27 |
| Cabbage | Start seeds indoors (spring) | Mar 10 – Apr 7 |
| Cabbage | Transplant outdoors (spring) | Apr 7 – May 8 |
| Cabbage | Start seeds indoors (fall) | Jun 6 – Jul 6 |
| Cabbage | Transplant outdoors (fall) | Jul 6 – Aug 6 |
| Leaf lettuce | Sow outdoors (spring) | Apr 7 – Jun 23 |
| Leaf lettuce | Sow outdoors (fall) | Jul 6 – Aug 22 |
| Spinach | Sow outdoors (spring) | Mar 31 – May 14 |
| Spinach | Sow outdoors (fall) | Jul 23 – Aug 27 |
| Radishes | Sow outdoors (spring) | Apr 7 – May 28 |
| Radishes | Sow outdoors (fall) | Jul 6 – Sep 6 |
| Kale | Sow outdoors (spring) | Apr 24 – May 14 |
| Kale | Sow outdoors (fall) | Jun 29 – Aug 6 |
| Carrots | Sow outdoors (spring) | May 8 – Jun 23 |
| Carrots | Sow outdoors (fall) | Jun 6 – Jul 22 |
| Garlic | Plant outdoors (fall) | Oct 6 – Nov 6 |
Where these dates come from
ZIP code 48721 is matched to the NOAA station Harrisville 2Nne, MI, 15.4 km away, at 585 ft elevation (25 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Harrisville 2Nne, MI (used) | 585 ft | May 8 | Oct 16 |
| Alpena Wwtp, MI | 590 ft | May 5 | Oct 17 |
| Alpena Co Rgnl Ap, MI | 684 ft | May 17 | Oct 1 |
| Glennie 2Se, MI | 894 ft | May 19 | Sep 29 |
Frost dates near Black River
- Lincoln, MI 48742 · last May 8, first Oct 16
- Spruce, MI 48762 · last May 8, first Oct 16
- Ossineke, MI 49766 · last May 17, first Oct 1
- Harrisville, MI 48740 · last May 8, first Oct 16
- Hubbard Lake, MI 49747 · last May 17, first Oct 1
- Barton City, MI 48705 · last May 16, first Oct 5
- Mikado, MI 48745 · last May 8, first Oct 16
- Greenbush, MI 48738 · last May 8, first Oct 16
Frequently asked questions
- When is the last frost in Black River, MI?
- For ZIP code 48721, the average last spring frost (32°F) is May 8, based on NOAA 1991-2020 climate normals for the Harrisville 2Nne, MI weather station. There is a 1-in-10 chance of a frost after May 24.
- When is the first frost in Black River, MI?
- The average first fall frost (32°F) is October 16. There is a 1-in-10 chance of frost by October 2, so tender plants are at risk from that point on.
- How long is the growing season in 48721?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 160 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.