| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 21°F | 33°F | 26°F | 1.9" |
| February | 27°F | 42°F | 33°F | 1.7" |
| March | 33°F | 52°F | 41°F | 2.8" |
| April | 37°F | 58°F | 46°F | 1.7" |
| May | 45°F | 68°F | 56°F | 3.6" |
| June | 49°F | 73°F | 60°F | 4.6" |
| July | 58°F | 87°F | 72°F | 2.3" |
| August | 54°F | 84°F | 68°F | 5.4" |
| September | 45°F | 72°F | 58°F | 1.1" |
| October | 38°F | 58°F | 46°F | 2.6" |
| November | 28°F | 41°F | 34°F | 2.2" |
| December | 21°F | 31°F | 26°F | 4.5" |
| Index | Harrington | Washington | National |
| Air quality index | 43 | 36 | 42 |
| Pollution index | 2,683,410 | 4,541,850 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 252 |
| Days with moderate air quality | 111 |
| Days w/ poor A.Q. for sensitive groups | 2 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.000% |
| Benzene | 0.040% |
| Carbon Tetrachloride | 0.004% |
| Lead | 0.030% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| Davenport, WA | 1,907 | 43 | 14.0% |
| Sprague, WA | 524 | 43 | 14.0% |
| Harrington, WA | 390 | 43 | 14.0% |
| City | Population | Air Quality Index | National Avg. |
| Nances Creek, AL | 390 | 43 | 14.0% |
| Turin, GA | 390 | 52 | 4.0% |
| Fort Atkinson, IA | 390 | 39 | 22.0% |
| Lee, IL | 390 | 0 | 100.0% |
| Hall Summit, LA | 390 | 39 | 22.0% |
| Harrington, WA | 390 | 43 | 14.0% |