Frost dates for 49902Alpha, MI
The average last spring frost in Alpha is May 24 and the average first fall frost is September 25, giving a typical growing season of about 121 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 24
- Average first fall frost
- Sep 25
- Growing season
- 121 days
Safer after Jun 8 (1-in-10 risk)
Possible by Sep 7 (1-in-10 risk)
Last frost typically in 210 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 5 · Jun 24 | Aug 24 · Sep 10 · Sep 27 | 93 days | 100% |
| Frost / freeze (32°F) | May 9 · May 24 · Jun 8 | Sep 7 · Sep 25 · Oct 9 | 121 days | 100% |
| Hard freeze (28°F) | Apr 27 · May 11 · May 26 | Sep 21 · Oct 6 · Oct 20 | 146 days | 100% |
Planting calendar for Alpha
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 5 |
| 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 15 |
| Summer squash | Sow outdoors | Jun 9 – Jul 24 |
| Winter squash & pumpkins | Sow outdoors | Jun 23 – Jul 24 |
| Snap beans | Sow outdoors | Jun 9 – Jul 8 |
| Sweet corn | Sow outdoors | Jun 9 – Jun 5 |
| 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 26 – Jun 5 |
| Broccoli | Transplant outdoors (fall) | Jun 25 – Jul 6 |
| Cabbage | Start seeds indoors (spring) | Mar 26 – Apr 23 |
| Cabbage | Transplant outdoors (spring) | Apr 23 – May 24 |
| Cabbage | Start seeds indoors (fall) | May 16 – Jun 15 |
| Cabbage | Transplant outdoors (fall) | Jun 15 – Jul 16 |
| Leaf lettuce | Sow outdoors (spring) | Apr 23 – Jul 9 |
| Leaf lettuce | Sow outdoors (fall) | Jun 15 – Aug 1 |
| Spinach | Sow outdoors (spring) | Apr 16 – May 30 |
| Spinach | Sow outdoors (fall) | Jul 2 – Aug 6 |
| Radishes | Sow outdoors (spring) | Apr 23 – Jun 13 |
| Radishes | Sow outdoors (fall) | Jun 15 – Aug 16 |
| Kale | Sow outdoors (spring) | May 10 – May 30 |
| Kale | Sow outdoors (fall) | Jun 8 – Jul 16 |
| Carrots | Sow outdoors (spring) | May 24 – Jul 9 |
| Carrots | Sow outdoors (fall) | May 16 – Jul 1 |
| Garlic | Plant outdoors (fall) | Sep 15 – Oct 16 |
Where these dates come from
ZIP code 49902 is matched to the NOAA station Florence, WI, 15.3 km away, at 1,300 ft elevation (117 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Florence, WI (used) | 1,300 ft | May 24 | Sep 25 |
| Stambaugh 2Sse, MI | 1,450 ft | Jun 4 | Sep 10 |
| Amasa 1W, MI | 1,470 ft | Jun 6 | Sep 9 |
| Iron Mtn Ford Ap, MI | 1,149 ft | May 25 | Sep 24 |
Frost dates near Alpha
- Crystal Falls, MI 49920 · last Jun 6, first Sep 9
- Gaastra, MI 49927 · last Jun 4, first Sep 10
- Florence, WI 54121 · last May 24, first Sep 25
- Stambaugh, MI 49964 · last Jun 4, first Sep 10
- Caspian, MI 49915 · last Jun 4, first Sep 10
- Iron River, MI 49935 · last Jun 4, first Sep 10
- Amasa, MI 49903 · last Jun 6, first Sep 9
- Long Lake, WI 54542 · last Jun 4, first Sep 10
Frequently asked questions
- When is the last frost in Alpha, MI?
- For ZIP code 49902, the average last spring frost (32°F) is May 24, based on NOAA 1991-2020 climate normals for the Florence, WI weather station. There is a 1-in-10 chance of a frost after June 8.
- When is the first frost in Alpha, MI?
- The average first fall frost (32°F) is September 25. There is a 1-in-10 chance of frost by September 7, so tender plants are at risk from that point on.
- How long is the growing season in 49902?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 121 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.