| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 22°F | 38°F | 30°F | 2.9" |
| February | 23°F | 40°F | 30°F | 2.0" |
| March | 32°F | 52°F | 41°F | 3.5" |
| April | 42°F | 65°F | 53°F | 3.3" |
| May | 51°F | 73°F | 62°F | 4.2" |
| June | 59°F | 80°F | 69°F | 4.5" |
| July | 63°F | 84°F | 73°F | 3.6" |
| August | 62°F | 83°F | 72°F | 3.9" |
| September | 55°F | 77°F | 65°F | 3.3" |
| October | 45°F | 65°F | 54°F | 3.6" |
| November | 35°F | 54°F | 44°F | 2.6" |
| December | 27°F | 43°F | 34°F | 3.6" |
| Index | Brilliant | Ohio | National |
| Air quality index | 46 | 40 | 42 |
| Pollution index | 1,410,280 | 4,472,386 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 217 |
| Days with moderate air quality | 144 |
| Days w/ poor A.Q. for sensitive groups | 4 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.002% |
| Benzene | 0.010% |
| Carbon Tetrachloride | 0.002% |
| Lead | 0.001% |
| Mercury | 0.004% |
| City | Population | Air Quality Index | National Avg. |
| Martins Ferry, OH | 6,589 | 39 | 22.0% |
| Yorkville, OH | 1,013 | 39 | 22.0% |
| Rayland, OH | 481 | 39 | 22.0% |
| Wheeling, WV | 27,046 | 39 | 22.0% |
| Adena, OH | 682 | 39 | 22.0% |
| Brilliant, OH | 1,302 | 46 | 8.0% |
| City | Population | Air Quality Index | National Avg. |
| Westhaven-Moonstone, CA | 1,302 | 27 | 46.0% |
| Nelson, GA | 1,302 | 37 | 26.0% |
| Jonesboro, IN | 1,302 | 35 | 30.0% |
| Labadieville, LA | 1,302 | 41 | 18.0% |
| L'Isle-aux-Allumettes, QC | 1,302 | n/a | |
| Brilliant, OH | 1,302 | 46 | 8.0% |
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