Frost dates for 48104Ann Arbor, MI
The average last spring frost in Ann Arbor is May 5 and the average first fall frost is October 10, giving a typical growing season of about 157 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 5
- Average first fall frost
- Oct 10
- Growing season
- 157 days
Safer after May 20 (1-in-10 risk)
Possible by Sep 28 (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 1 · May 15 · May 29 | Sep 18 · Oct 1 · Oct 12 | 137 days | 100% |
| Frost / freeze (32°F) | Apr 21 · May 5 · May 20 | Sep 28 · Oct 10 · Oct 24 | 157 days | 100% |
| Hard freeze (28°F) | Apr 10 · Apr 24 · May 11 | Oct 7 · Oct 23 · Nov 6 | 180 days | 100% |
Planting calendar for Ann Arbor
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 20 |
| 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 – Jun 30 |
| Summer squash | Sow outdoors | May 21 – Jul 5 |
| Winter squash & pumpkins | Sow outdoors | Jun 4 – Jul 5 |
| Snap beans | Sow outdoors | May 21 – Jul 23 |
| Sweet corn | Sow outdoors | May 21 – Jun 20 |
| 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 10 – Jun 20 |
| Broccoli | Transplant outdoors (fall) | Jul 10 – Jul 21 |
| Cabbage | Start seeds indoors (spring) | Mar 7 – Apr 4 |
| Cabbage | Transplant outdoors (spring) | Apr 4 – May 5 |
| Cabbage | Start seeds indoors (fall) | May 31 – Jun 30 |
| Cabbage | Transplant outdoors (fall) | Jun 30 – Jul 31 |
| Leaf lettuce | Sow outdoors (spring) | Apr 4 – Jun 20 |
| Leaf lettuce | Sow outdoors (fall) | Jun 30 – Aug 16 |
| Spinach | Sow outdoors (spring) | Mar 28 – May 11 |
| Spinach | Sow outdoors (fall) | Jul 17 – Aug 21 |
| Radishes | Sow outdoors (spring) | Apr 4 – May 25 |
| Radishes | Sow outdoors (fall) | Jun 30 – Aug 31 |
| Kale | Sow outdoors (spring) | Apr 21 – May 11 |
| Kale | Sow outdoors (fall) | Jun 23 – Jul 31 |
| Carrots | Sow outdoors (spring) | May 5 – Jun 20 |
| Carrots | Sow outdoors (fall) | May 31 – Jul 16 |
| Garlic | Plant outdoors (fall) | Sep 30 – Oct 31 |
Where these dates come from
ZIP code 48104 is matched to the NOAA station Ann Arbor Se, MI, 4.2 km away, at 832 ft elevation (44 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Ann Arbor Se, MI (used) | 832 ft | May 5 | Oct 10 |
| Ann Arbor Muni Ap, MI | 839 ft | May 8 | Oct 4 |
| Ann Arbor U Of Mich, MI | 813 ft | May 3 | Oct 13 |
| Saline Wwtp, MI | 750 ft | May 2 | Oct 11 |
Frost dates near Ann Arbor
- Ann Arbor, MI 48109 · last May 5, first Oct 10
- Ypsilanti, MI 48197 · last May 5, first Oct 10
- Saline, MI 48176 · last May 2, first Oct 11
- Dexter, MI 48130 · last Apr 30, first Oct 12
- Whitmore Lake, MI 48189 · last May 5, first Oct 13
- Bridgewater, MI 48115 · last Apr 30, first Oct 14
- Whittaker, MI 48190 · last May 3, first Oct 10
- Salem, MI 48175 · last May 3, first Oct 13
Frequently asked questions
- When is the last frost in Ann Arbor, MI?
- For ZIP code 48104, the average last spring frost (32°F) is May 5, based on NOAA 1991-2020 climate normals for the Ann Arbor Se, MI weather station. There is a 1-in-10 chance of a frost after May 20.
- When is the first frost in Ann Arbor, MI?
- The average first fall frost (32°F) is October 10. There is a 1-in-10 chance of frost by September 28, so tender plants are at risk from that point on.
- How long is the growing season in 48104?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 157 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.