| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 22°F | 41°F | 31°F | 2.7" |
| February | 22°F | 43°F | 32°F | 2.6" |
| March | 33°F | 57°F | 44°F | 4.4" |
| April | 43°F | 69°F | 55°F | 5.1" |
| May | 52°F | 77°F | 64°F | 4.4" |
| June | 61°F | 85°F | 73°F | 4.7" |
| July | 64°F | 87°F | 75°F | 3.7" |
| August | 62°F | 87°F | 74°F | 2.8" |
| September | 55°F | 81°F | 67°F | 3.8" |
| October | 43°F | 69°F | 55°F | 3.8" |
| November | 32°F | 57°F | 43°F | 3.1" |
| December | 27°F | 46°F | 36°F | 4.1" |
| Index | Fairfield | Ohio | National |
| Air quality index | 54 | 40 | 42 |
| Pollution index | 7,300,490 | 4,472,386 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 139 |
| Days with moderate air quality | 206 |
| Days w/ poor A.Q. for sensitive groups | 20 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.520% |
| Benzene | 0.070% |
| Carbon Tetrachloride | 0.040% |
| Lead | 0.240% |
| Mercury | 0.050% |
| City | Population | Air Quality Index | National Avg. |
| Darrtown, OH | 550 | 6 | 88.0% |
| Oxford, OH | 23,192 | 6 | 88.0% |
| Middletown, OH | 48,765 | 47 | 6.0% |
| Hunter, OH | 3,918 | 47 | 6.0% |
| Jacksonburg, OH | 51 | 47 | 6.0% |
| Fairfield, OH | 42,623 | 54 | 8.0% |
| City | Population | Air Quality Index | National Avg. |
| Burlington, VT | 42,645 | 37 | 26.0% |
| Farmers Branch, TX | 42,659 | 51 | 2.0% |
| Jefferson City, MO | 42,670 | 39 | 22.0% |
| Mankato, MN | 42,685 | 46 | 8.0% |
| Rohnert Park, CA | 42,559 | 34 | 32.0% |
| Fairfield, OH | 42,623 | 54 | 8.0% |
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