Ann Arbor weather by month
Ann Arbor runs from about -3°C in January to 22°C in July, with January the wettest month at 130 mm.
warmest month
July
22°C
coolest month
January
-3°C
wettest month
January
130 mm
worst air month
February
13 µg/m³
The whole year, month by month.
| Month | Avg temp | Rain | Sun | PM2.5 |
|---|---|---|---|---|
| January | -3°C | 130 mm | 102 h | 8 |
| February | 1°C | 8 mm | 243 h | 13 |
| March | 5°C | 59 mm | 213 h | 10 |
| April | 10°C | 116 mm | 286 h | 9 |
| May | 17°C | 68 mm | 366 h | 7 |
| June | 21°C | 69 mm | 349 h | 7 |
| July | 22°C | 101 mm | 382 h | 12 |
| August | 21°C | 70 mm | 357 h | 12 |
| September | 19°C | 39 mm | 280 h | 10 |
| October | 12°C | 36 mm | 291 h | 6 |
| November | 7°C | 54 mm | 142 h | 6 |
| December | 0°C | 85 mm | 116 h | 8 |
About 3,127 hours of sun a year. Roughly 85 rainy days a year.
These are long-run climate normals, not a forecast. A given year can sit well outside them. PM2.5 is a global model: near the coast it counts sea salt as fine particulate and reads high against ground stations, sometimes by a factor of two. Use the shape of the year, not the absolute number.
where these numbers come from
- · Temperature, rainfall and sunshine: ECMWF ERA5 reanalysis climate normals via Open-Meteo (CC BY 4.0), fetched once and stored.
- · PM2.5: Copernicus CAMS reanalysis, monthly means. Modelled, not station readings; near coasts CAMS counts sea salt as PM2.5 and reads high.
Last reviewed 2026-05-24. Full method, licences and the list of sources we rejected are on the methodology page.