| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 25°F | 45°F | 34°F | 3.8" |
| February | 26°F | 48°F | 36°F | 3.1" |
| March | 36°F | 60°F | 48°F | 4.7" |
| April | 45°F | 72°F | 59°F | 5.9" |
| May | 55°F | 79°F | 67°F | 4.9" |
| June | 64°F | 88°F | 76°F | 4.3" |
| July | 67°F | 90°F | 78°F | 5.2" |
| August | 66°F | 90°F | 77°F | 3.2" |
| September | 58°F | 84°F | 70°F | 4.2" |
| October | 46°F | 73°F | 59°F | 3.9" |
| November | 35°F | 60°F | 47°F | 4.1" |
| December | 29°F | 48°F | 38°F | 4.8" |
| Index | Somerville | Indiana | National |
| Air quality index | 45 | 56 | 42 |
| Pollution index | 4,793,970 | 2,719,453 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 244 |
| Days with moderate air quality | 111 |
| Days w/ poor A.Q. for sensitive groups | 10 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.310% |
| Benzene | 0.010% |
| Carbon Tetrachloride | 0.001% |
| Lead | 0.120% |
| Mercury | 0.140% |
| City | Population | Air Quality Index | National Avg. |
| Petersburg, IN | 2,315 | 1 | 98.0% |
| Winslow, IN | 900 | 6 | 88.0% |
| Spurgeon, IN | 123 | 6 | 88.0% |
| Oakland City, IN | 2,570 | 6 | 88.0% |
| Francisco, IN | 541 | 36 | 28.0% |
| Somerville, IN | 354 | 45 | 10.0% |
| City | Population | Air Quality Index | National Avg. |
| Rock City, IL | 354 | 42 | 16.0% |
| Everest, KS | 354 | 43 | 14.0% |
| Greeley, KS | 354 | 41 | 18.0% |
| Uniontown, KS | 354 | 37 | 26.0% |
| Otterville, MO | 354 | 38 | 24.0% |
| Somerville, IN | 354 | 45 | 10.0% |
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