| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 23°F | 41°F | 31°F | 3.4" |
| February | 24°F | 44°F | 33°F | 5.0" |
| March | 32°F | 55°F | 43°F | 4.1" |
| April | 41°F | 67°F | 53°F | 5.5" |
| May | 49°F | 73°F | 61°F | 6.4" |
| June | 57°F | 80°F | 68°F | 6.5" |
| July | 61°F | 82°F | 71°F | 5.2" |
| August | 60°F | 82°F | 70°F | 4.8" |
| September | 54°F | 76°F | 64°F | 5.1" |
| October | 42°F | 66°F | 53°F | 7.3" |
| November | 32°F | 55°F | 42°F | 3.9" |
| December | 28°F | 46°F | 36°F | 4.8" |
| Index | Union | West Virginia | National |
| Air quality index | 41 | 126 | 42 |
| Pollution index | 2,390,880 | 1,996,538 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 306 |
| Days with moderate air quality | 55 |
| Days w/ poor A.Q. for sensitive groups | 4 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.010% |
| Benzene | 0.010% |
| Carbon Tetrachloride | 0.002% |
| Lead | 0.010% |
| Mercury | 0.020% |
| City | Population | Air Quality Index | National Avg. |
| Peterstown, WV | 752 | 41 | 18.0% |
| Fairlea, WV | 1,857 | 41 | 18.0% |
| Ronceverte, WV | 1,626 | 41 | 18.0% |
| White Sulphur Springs, WV | 3,051 | 41 | 18.0% |
| Alderson, WV | 1,074 | 295 | 490.0% |
| Union, WV | 459 | 41 | 18.0% |
| City | Population | Air Quality Index | National Avg. |
| Kwethluk, AK | 459 | 31 | 38.0% |
| Silas, AL | 459 | 36 | 28.0% |
| Lexington, GA | 459 | 44 | 12.0% |
| Elkhart, IL | 459 | 40 | 20.0% |
| Coatesville, IN | 459 | 54 | 8.0% |
| Union, WV | 459 | 41 | 18.0% |
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