Frost dates for 48191Willis, MI
The average last spring frost in Willis is May 3 and the average first fall frost is October 10, giving a typical growing season of about 158 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 3
- Average first fall frost
- Oct 10
- Growing season
- 158 days
Safer after May 25 (1-in-10 risk)
Possible by Sep 25 (1-in-10 risk)
Last frost typically in 181 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) | Apr 30 · May 17 · Jun 4 | Sep 14 · Sep 30 · Oct 12 | 134 days | 100% |
| Frost / freeze (32°F) | Apr 17 · May 3 · May 25 | Sep 25 · Oct 10 · Oct 25 | 158 days | 100% |
| Hard freeze (28°F) | Apr 6 · Apr 22 · May 12 | Oct 5 · Oct 23 · Nov 7 | 183 days | 100% |
Planting calendar for Willis
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 2 – Jun 8 |
| Tomatoes | Transplant outdoors | May 19 – Jun 20 |
| Peppers | Start seeds indoors | Apr 2 – May 3 |
| Peppers | Transplant outdoors | Jun 2 – Jul 3 |
| Eggplant | Start seeds indoors | Apr 19 – May 18 |
| Eggplant | Transplant outdoors | Jun 2 – Jul 3 |
| Cucumbers | Sow outdoors | Jun 2 – Jun 30 |
| Summer squash | Sow outdoors | May 19 – Jul 3 |
| Winter squash & pumpkins | Sow outdoors | Jun 2 – Jul 3 |
| Snap beans | Sow outdoors | May 19 – Jul 23 |
| Sweet corn | Sow outdoors | May 19 – Jun 20 |
| Watermelon & cantaloupe | Sow outdoors | Jun 2 – Jul 3 |
| Okra | Sow outdoors | May 26 – Jun 18 |
| Peas | Sow outdoors (spring) | Apr 2 – May 18 |
| Potatoes | Plant outdoors (spring) | Apr 2 – Jun 2 |
| Onions | Start seeds indoors (spring) | Feb 19 – Mar 18 |
| Onions | Transplant outdoors (spring) | Apr 19 – May 18 |
| Broccoli | Start seeds indoors (spring) | Mar 15 – Apr 18 |
| Broccoli | Transplant outdoors (spring) | Apr 19 – May 18 |
| Broccoli | Start seeds indoors (fall) | Jun 10 – Jun 20 |
| Broccoli | Transplant outdoors (fall) | Jul 10 – Jul 21 |
| Cabbage | Start seeds indoors (spring) | Mar 5 – Apr 2 |
| Cabbage | Transplant outdoors (spring) | Apr 2 – May 3 |
| Cabbage | Start seeds indoors (fall) | May 31 – Jun 30 |
| Cabbage | Transplant outdoors (fall) | Jun 30 – Jul 31 |
| Leaf lettuce | Sow outdoors (spring) | Apr 2 – Jun 18 |
| Leaf lettuce | Sow outdoors (fall) | Jun 30 – Aug 16 |
| Spinach | Sow outdoors (spring) | Mar 26 – May 9 |
| Spinach | Sow outdoors (fall) | Jul 17 – Aug 21 |
| Radishes | Sow outdoors (spring) | Apr 2 – May 23 |
| Radishes | Sow outdoors (fall) | Jun 30 – Aug 31 |
| Kale | Sow outdoors (spring) | Apr 19 – May 9 |
| Kale | Sow outdoors (fall) | Jun 23 – Jul 31 |
| Carrots | Sow outdoors (spring) | May 3 – Jun 18 |
| Carrots | Sow outdoors (fall) | May 31 – Jul 16 |
| Garlic | Plant outdoors (fall) | Sep 30 – Oct 31 |
Where these dates come from
ZIP code 48191 is matched to the NOAA station Milan 4 Ese, MI, 8.1 km away, at 670 ft elevation (6 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Milan 4 Ese, MI (used) | 670 ft | May 3 | Oct 10 |
| Milan Wwtp, MI | 680 ft | Apr 26 | Oct 19 |
| Detroit Willow Run Ap, MI | 777 ft | Apr 24 | Oct 24 |
| Carleton 2W, MI | 627 ft | Apr 27 | Oct 20 |
Frost dates near Willis
- Whittaker, MI 48190 · last May 3, first Oct 10
- Milan, MI 48160 · last May 3, first Oct 10
- Belleville, MI 48111 · last Apr 24, first Oct 24
- Maybee, MI 48159 · last May 3, first Oct 10
- Ypsilanti, MI 48197 · last May 5, first Oct 10
- Azalia, MI 48110 · last Apr 27, first Oct 21
- Ann Arbor, MI 48108 · last May 5, first Oct 10
- New Boston, MI 48164 · last Apr 20, first Oct 27
Frequently asked questions
- When is the last frost in Willis, MI?
- For ZIP code 48191, the average last spring frost (32°F) is May 3, based on NOAA 1991-2020 climate normals for the Milan 4 Ese, MI weather station. There is a 1-in-10 chance of a frost after May 25.
- When is the first frost in Willis, MI?
- The average first fall frost (32°F) is October 10. There is a 1-in-10 chance of frost by September 25, so tender plants are at risk from that point on.
- How long is the growing season in 48191?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 158 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.