| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 19°F | 43°F | 30°F | 3.2" |
| February | 20°F | 44°F | 31°F | 2.5" |
| March | 29°F | 56°F | 41°F | 4.0" |
| April | 37°F | 68°F | 52°F | 4.6" |
| May | 46°F | 74°F | 59°F | 4.8" |
| June | 55°F | 81°F | 67°F | 4.8" |
| July | 59°F | 83°F | 70°F | 6.2" |
| August | 58°F | 83°F | 69°F | 4.2" |
| September | 51°F | 78°F | 63°F | 3.3" |
| October | 40°F | 67°F | 52°F | 4.1" |
| November | 29°F | 57°F | 41°F | 2.8" |
| December | 24°F | 47°F | 35°F | 4.4" |
| Index | Helvetia | West Virginia | National |
| Air quality index | 31 | 126 | 42 |
| Pollution index | 11,851,300 | 1,996,538 | 2,726,193 |
| Measurement | Total |
| Days measured | 111 |
| Days with good air quality | 101 |
| Days with moderate air quality | 10 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.090% |
| Benzene | 0.010% |
| Carbon Tetrachloride | 0.002% |
| Lead | 0.020% |
| Mercury | 0.720% |
| City | Population | Air Quality Index | National Avg. |
| Valley Bend, WV | 634 | 31 | 38.0% |
| Womelsdorf (Coalton), WV | 194 | 31 | 38.0% |
| Huttonsville, WV | 129 | 31 | 38.0% |
| Pickens, WV | 19 | 31 | 38.0% |
| Mill Creek, WV | 843 | 31 | 38.0% |
| Helvetia, WV | 84 | 31 | 38.0% |
| City | Population | Air Quality Index | National Avg. |
| Blue Springs, AL | 84 | 35 | 30.0% |
| Graham, AL | 84 | 38 | 24.0% |
| Moccasin, AZ | 84 | 44 | 12.0% |
| Sierra City, CA | 84 | 44 | 12.0% |
| Joes, CO | 84 | 58 | 16.0% |
| Helvetia, WV | 84 | 31 | 38.0% |
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