| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 22°F | 39°F | 30°F | 2.9" |
| February | 22°F | 40°F | 31°F | 2.3" |
| March | 34°F | 55°F | 44°F | 3.8" |
| April | 44°F | 68°F | 55°F | 5.1" |
| May | 54°F | 77°F | 65°F | 4.6" |
| June | 63°F | 85°F | 73°F | 6.3" |
| July | 64°F | 86°F | 75°F | 4.4" |
| August | 62°F | 85°F | 73°F | 3.0" |
| September | 56°F | 80°F | 67°F | 3.6" |
| October | 45°F | 68°F | 56°F | 3.5" |
| November | 34°F | 55°F | 44°F | 3.5" |
| December | 27°F | 43°F | 34°F | 4.1" |
| Index | Westport | Indiana | National |
| Air quality index | 41 | 56 | 42 |
| Pollution index | 1,370,100 | 2,719,453 | 2,726,193 |
| Measurement | Total |
| Days measured | 364 |
| Days with good air quality | 298 |
| Days with moderate air quality | 66 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.040% |
| Benzene | 0.020% |
| Carbon Tetrachloride | 0.002% |
| Lead | 0.001% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| Hayden, IN | 542 | 35 | 30.0% |
| Holton, IN | 683 | 35 | 30.0% |
| Country Squire Lakes, IN | 3,220 | 35 | 30.0% |
| North Vernon, IN | 7,167 | 35 | 30.0% |
| Vernon, IN | 196 | 35 | 30.0% |
| Westport, IN | 1,250 | 41 | 18.0% |
| City | Population | Air Quality Index | National Avg. |
| Altoona, AL | 1,250 | 43 | 14.0% |
| Upper Lake, CA | 1,250 | 33 | 34.0% |
| Pandora, OH | 1,250 | 39 | 22.0% |
| Tellico Plains, TN | 1,250 | 30 | 40.0% |
| Loyal, WI | 1,250 | 34 | 32.0% |
| Westport, IN | 1,250 | 41 | 18.0% |
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