Frost dates for 49707Alpena, MI
The average last spring frost in Alpena is May 5 and the average first fall frost is October 17, giving a typical growing season of about 163 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 5
- Average first fall frost
- Oct 17
- Growing season
- 163 days
Safer after May 21 (1-in-10 risk)
Possible by Sep 30 (1-in-10 risk)
Last frost typically in 184 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 2 · May 17 · May 30 | Sep 20 · Oct 4 · Oct 19 | 141 days | 100% |
| Frost / freeze (32°F) | Apr 21 · May 5 · May 21 | Sep 30 · Oct 17 · Nov 1 | 163 days | 100% |
| Hard freeze (28°F) | Apr 7 · Apr 23 · May 13 | Oct 15 · Oct 31 · Nov 15 | 190 days | 100% |
Planting calendar for Alpena
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 4 – Jun 10 |
| Tomatoes | Transplant outdoors | May 21 – Jun 27 |
| Peppers | Start seeds indoors | Apr 4 – May 5 |
| Peppers | Transplant outdoors | Jun 4 – Jul 5 |
| Eggplant | Start seeds indoors | Apr 21 – May 20 |
| Eggplant | Transplant outdoors | Jun 4 – Jul 5 |
| Cucumbers | Sow outdoors | Jun 4 – Jul 7 |
| Summer squash | Sow outdoors | May 21 – Jul 5 |
| Winter squash & pumpkins | Sow outdoors | Jun 4 – Jul 5 |
| Snap beans | Sow outdoors | May 21 – Jul 30 |
| Sweet corn | Sow outdoors | May 21 – Jun 27 |
| Watermelon & cantaloupe | Sow outdoors | Jun 4 – Jul 5 |
| Okra | Sow outdoors | May 28 – Jun 20 |
| Peas | Sow outdoors (spring) | Apr 4 – May 20 |
| Potatoes | Plant outdoors (spring) | Apr 4 – Jun 4 |
| Onions | Start seeds indoors (spring) | Feb 21 – Mar 20 |
| Onions | Transplant outdoors (spring) | Apr 21 – May 20 |
| Broccoli | Start seeds indoors (spring) | Mar 17 – Apr 20 |
| Broccoli | Transplant outdoors (spring) | Apr 21 – May 20 |
| Broccoli | Start seeds indoors (fall) | Jun 17 – Jun 27 |
| Broccoli | Transplant outdoors (fall) | Jul 17 – Jul 28 |
| Cabbage | Start seeds indoors (spring) | Mar 7 – Apr 4 |
| Cabbage | Transplant outdoors (spring) | Apr 4 – May 5 |
| Cabbage | Start seeds indoors (fall) | Jun 7 – Jul 7 |
| Cabbage | Transplant outdoors (fall) | Jul 7 – Aug 7 |
| Leaf lettuce | Sow outdoors (spring) | Apr 4 – Jun 20 |
| Leaf lettuce | Sow outdoors (fall) | Jul 7 – Aug 23 |
| Spinach | Sow outdoors (spring) | Mar 28 – May 11 |
| Spinach | Sow outdoors (fall) | Jul 24 – Aug 28 |
| Radishes | Sow outdoors (spring) | Apr 4 – May 25 |
| Radishes | Sow outdoors (fall) | Jul 7 – Sep 7 |
| Kale | Sow outdoors (spring) | Apr 21 – May 11 |
| Kale | Sow outdoors (fall) | Jun 30 – Aug 7 |
| Carrots | Sow outdoors (spring) | May 5 – Jun 20 |
| Carrots | Sow outdoors (fall) | Jun 7 – Jul 23 |
| Garlic | Plant outdoors (fall) | Oct 7 – Nov 7 |
Where these dates come from
ZIP code 49707 is matched to the NOAA station Alpena Wwtp, MI, 3.2 km away, at 590 ft elevation (20 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Alpena Wwtp, MI (used) | 590 ft | May 5 | Oct 17 |
| Alpena Co Rgnl Ap, MI | 684 ft | May 17 | Oct 1 |
| Alpena 10Nw, MI | 740 ft | May 13 | Oct 3 |
| Harrisville 2Nne, MI | 585 ft | May 8 | Oct 16 |
Frost dates near Alpena
- Herron, MI 49744 · last May 17, first Oct 1
- Ossineke, MI 49766 · last May 17, first Oct 1
- Posen, MI 49776 · last May 17, first Oct 1
- Lachine, MI 49753 · last May 17, first Oct 1
- Hubbard Lake, MI 49747 · last May 17, first Oct 1
- Presque Isle, MI 49777 · last May 10, first Oct 14
- Spruce, MI 48762 · last May 8, first Oct 16
- Black River, MI 48721 · last May 8, first Oct 16
Frequently asked questions
- When is the last frost in Alpena, MI?
- For ZIP code 49707, the average last spring frost (32°F) is May 5, based on NOAA 1991-2020 climate normals for the Alpena Wwtp, MI weather station. There is a 1-in-10 chance of a frost after May 21.
- When is the first frost in Alpena, MI?
- The average first fall frost (32°F) is October 17. There is a 1-in-10 chance of frost by September 30, so tender plants are at risk from that point on.
- How long is the growing season in 49707?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 163 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.