| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 19°F | 35°F | 27°F | 2.0" |
| February | 19°F | 35°F | 27°F | 1.8" |
| March | 29°F | 49°F | 38°F | 2.9" |
| April | 40°F | 62°F | 50°F | 3.6" |
| May | 51°F | 74°F | 62°F | 3.8" |
| June | 61°F | 83°F | 71°F | 4.1" |
| July | 64°F | 86°F | 75°F | 4.2" |
| August | 63°F | 84°F | 73°F | 3.7" |
| September | 56°F | 77°F | 66°F | 3.6" |
| October | 45°F | 65°F | 54°F | 2.5" |
| November | 34°F | 52°F | 43°F | 2.6" |
| December | 25°F | 40°F | 32°F | 2.6" |
| Index | Helena | Ohio | National |
| Air quality index | 40 | 40 | 42 |
| Pollution index | 2,402,580 | 4,472,386 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 291 |
| Days with moderate air quality | 73 |
| Days w/ poor A.Q. for sensitive groups | 1 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.001% |
| Benzene | 0.020% |
| Carbon Tetrachloride | 0.005% |
| Lead | 0.020% |
| Mercury | 0.003% |
| City | Population | Air Quality Index | National Avg. |
| Bettsville, OH | 762 | 40 | 20.0% |
| Old Fort, OH | 218 | 40 | 20.0% |
| Oak Harbor, OH | 2,708 | 40 | 20.0% |
| Risingsun, OH | 515 | 40 | 20.0% |
| Fremont, OH | 16,005 | 40 | 20.0% |
| Helena, OH | 269 | 40 | 20.0% |
| City | Population | Air Quality Index | National Avg. |
| Tuluksak, AK | 269 | 31 | 38.0% |
| Akron, AL | 269 | 35 | 30.0% |
| Axis, AL | 269 | 42 | 16.0% |
| Parkdale, AR | 269 | 34 | 32.0% |
| Midland, CO | 269 | 45 | 10.0% |
| Helena, OH | 269 | 40 | 20.0% |
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