Frost dates by ZIP code: The nearest NOAA stations to your ZIP, 1991-2020 normals
Enter a five-digit ZIP code. PlainClimate finds its center (Census Bureau 2024) and the five nearest NOAA stations with frost dates, and shows each station's last spring and first autumn 32°F dates with its distance and elevation.
Frost dates near ZIP 48109
The USDA's 2023 Plant Hardiness Zone Map puts ZIP 48109 in zone 6a (the coldest night of a typical year: -10 to -5°F).
The nearest station, Ann Arbor University of Michigan, MI, is 2 miles from the ZIP's center: its last spring frost comes after May 3 in half of years and after May 20 in one year in ten. By the USDA's method its plant hardiness zone is 6a.
| Station | Distance | Elevation | Last frost (median) | 1 in 10 after | First frost (median) | Hardiness zone |
|---|---|---|---|---|---|---|
| Ann Arbor University of Michigan, MI | 2 mi | 813 ft | May 3 | May 20 | October 13 | 6a |
| Ann Arbor SE, MI | 4 mi | 832 ft | May 5 | May 20 | October 10 | 6a |
| Ann Arbor, MIAnn Arbor Municipal Airport | 5 mi | 839 ft | May 8 | May 26 | October 4 | 5b |
| Saline, MISaline Wastewater Treatment Plant | 10 mi | 750 ft | May 2 | May 18 | October 11 | – |
| Detroit Willow Run Airport, MI | 10 mi | 777 ft | April 24 | May 11 | October 24 | 6a |
Frost comes later in spring at higher and colder stations and earlier in low, open ground: prefer a station at a similar elevation to yours. Hardiness zone in the table: the USDA's rule (the average of each year's coldest night, 1991-2020) applied to the station's own record.
Every frost threshold at Ann Arbor University of Michigan
NOAA publishes the dates for several temperatures and odds. A 30% spring date means a 3-in-10 chance of a later frost (the convention almanacs use); 50% is the median; 10% the cautious date.
| Threshold | Spring, 10% | Spring, 30% | Spring, 50% | Spring, 90% | Autumn, 50% | Autumn, 10% |
|---|---|---|---|---|---|---|
| 36°F (light frost) | May 31 | May 23 | May 16 | April 30 | October 2 | September 20 |
| 32°F | May 20 | May 10 | May 3 | April 20 | October 13 | September 29 |
| 28°F (hard freeze) | May 9 | April 29 | April 23 | April 9 | October 26 | October 12 |
| 24°F | April 26 | April 17 | April 11 | March 30 | November 6 | October 25 |
Source: NOAA NCEI 1991-2020 annual normals; ZIP centers: Census Bureau 2024 Gazetteer; USDA 2023 Plant Hardiness Zone Map, ZIP listings: PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed October 8, 2026. Autumn 10%: one year in ten has its first frost before this date.