| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 24°F | 42°F | 32°F | 3.4" |
| February | 25°F | 44°F | 33°F | 2.6" |
| March | 34°F | 56°F | 44°F | 3.9" |
| April | 43°F | 69°F | 56°F | 4.2" |
| May | 52°F | 76°F | 63°F | 4.1" |
| June | 60°F | 83°F | 71°F | 4.9" |
| July | 64°F | 85°F | 74°F | 4.8" |
| August | 63°F | 86°F | 73°F | 3.6" |
| September | 56°F | 80°F | 67°F | 3.2" |
| October | 45°F | 68°F | 55°F | 3.7" |
| November | 35°F | 57°F | 45°F | 2.9" |
| December | 29°F | 46°F | 37°F | 4.2" |
| Index | Grantsville | West Virginia | National |
| Air quality index | 35 | 126 | 42 |
| Pollution index | 231,791 | 1,996,538 | 2,726,193 |
| Measurement | Total |
| Days measured | 364 |
| Days with good air quality | 333 |
| Days with moderate air quality | 31 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.000% |
| Benzene | 0.003% |
| Carbon Tetrachloride | 0.001% |
| Lead | 0.000% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| Glenville, WV | 1,507 | 31 | 38.0% |
| Auburn, WV | 96 | 31 | 38.0% |
| Spencer, WV | 2,096 | 35 | 30.0% |
| Grantsville, WV | 528 | 35 | 30.0% |
| City | Population | Air Quality Index | National Avg. |
| Nezperce, ID | 528 | 29 | 42.0% |
| Strasburg, IL | 528 | 40 | 20.0% |
| Bancroft, KY | 528 | 49 | 2.0% |
| Gem Lake, MN | 528 | 46 | 8.0% |
| Marston, MO | 528 | 26 | 48.0% |
| Grantsville, WV | 528 | 35 | 30.0% |
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