| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 19°F | 31°F | 25°F | 2.5" |
| February | 17°F | 31°F | 24°F | 1.9" |
| March | 24°F | 42°F | 33°F | 3.0" |
| April | 34°F | 55°F | 44°F | 5.6" |
| May | 44°F | 67°F | 55°F | 5.6" |
| June | 52°F | 74°F | 63°F | 6.3" |
| July | 57°F | 79°F | 68°F | 5.3" |
| August | 56°F | 77°F | 67°F | 5.4" |
| September | 50°F | 71°F | 60°F | 5.5" |
| October | 40°F | 59°F | 49°F | 6.3" |
| November | 32°F | 47°F | 39°F | 3.4" |
| December | 23°F | 34°F | 29°F | 2.8" |
| Index | Wellston | Michigan | National |
| Air quality index | 36 | 69 | 42 |
| Pollution index | 2,391,480 | 4,161,606 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 330 |
| Days with moderate air quality | 35 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.110% |
| Benzene | 0.020% |
| Carbon Tetrachloride | 0.002% |
| Lead | 0.030% |
| Mercury | 0.040% |
| City | Population | Air Quality Index | National Avg. |
| Mesick, MI | 381 | 36 | 28.0% |
| Free Soil, MI | 99 | 36 | 28.0% |
| Onekama, MI | 380 | 36 | 28.0% |
| Brethren, MI | 411 | 36 | 28.0% |
| Harrietta, MI | 224 | 36 | 28.0% |
| Wellston, MI | 262 | 36 | 28.0% |
| City | Population | Air Quality Index | National Avg. |
| Dry Creek, AK | 262 | 38 | 24.0% |
| Mekoryuk, AK | 262 | 31 | 38.0% |
| Oden, AR | 262 | 38 | 24.0% |
| Valle, AZ | 262 | 45 | 10.0% |
| Grand Lake, CO | 262 | 47 | 6.0% |
| Wellston, MI | 262 | 36 | 28.0% |
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