| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 22°F | 41°F | 31°F | 5.1" |
| February | 23°F | 44°F | 33°F | 2.7" |
| March | 34°F | 56°F | 44°F | 5.9" |
| April | 46°F | 69°F | 57°F | 6.6" |
| May | 55°F | 76°F | 65°F | 7.1" |
| June | 64°F | 85°F | 74°F | 10.2" |
| July | 64°F | 85°F | 74°F | 6.9" |
| August | 64°F | 85°F | 74°F | 8.4" |
| September | 57°F | 83°F | 69°F | 5.6" |
| October | 46°F | 71°F | 58°F | 6.1" |
| November | 35°F | 56°F | 44°F | 4.0" |
| December | 28°F | 44°F | 35°F | 5.5" |
| Index | Washington | Indiana | National |
| Air quality index | 1 | 56 | 42 |
| Pollution index | 1,698,620 | 2,719,453 | 2,726,193 |
| Measurement | Total |
| Days measured | 350 |
| Days with good air quality | 350 |
| Days with moderate air quality | 0 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.003% |
| Benzene | 0.030% |
| Carbon Tetrachloride | 0.002% |
| Lead | 0.080% |
| Mercury | 0.040% |
| City | Population | Air Quality Index | National Avg. |
| Elnora, IN | 519 | 1 | 98.0% |
| Edwardsport, IN | 308 | 1 | 98.0% |
| Plainville, IN | 275 | 1 | 98.0% |
| Bicknell, IN | 2,715 | 1 | 98.0% |
| Freelandville, IN | 759 | 1 | 98.0% |
| Washington, IN | 12,514 | 1 | 98.0% |
| City | Population | Air Quality Index | National Avg. |
| Wells Branch, TX | 12,512 | 44 | 12.0% |
| View Royal, BC | 12,511 | n/a | |
| Fords, NJ | 12,509 | 51 | 2.0% |
| Kincardine, ON | 12,522 | n/a | |
| Conneaut, OH | 12,524 | 34 | 32.0% |
| Washington, IN | 12,514 | 1 | 98.0% |
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