| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 22°F | 36°F | 28°F | 0.8" |
| February | 27°F | 45°F | 35°F | 0.5" |
| March | 32°F | 55°F | 43°F | 0.6" |
| April | 38°F | 64°F | 50°F | 0.5" |
| May | 47°F | 75°F | 61°F | 0.8" |
| June | 54°F | 81°F | 67°F | 0.9" |
| July | 62°F | 92°F | 78°F | 0.1" |
| August | 59°F | 89°F | 74°F | 0.1" |
| September | 50°F | 80°F | 65°F | 0.2" |
| October | 39°F | 63°F | 50°F | 0.6" |
| November | 30°F | 46°F | 38°F | 1.0" |
| December | 19°F | 34°F | 26°F | 1.2" |
| Index | Hartline | Washington | National |
| Air quality index | 18 | 36 | 42 |
| Pollution index | 2,683,410 | 4,541,850 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 339 |
| Days with moderate air quality | 26 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| 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. |
| Banks Lake South, WA | 113 | 18 | 64.0% |
| Coulee City, WA | 579 | 18 | 64.0% |
| Almira, WA | 267 | 18 | 64.0% |
| Hartline, WA | 182 | 18 | 64.0% |
| City | Population | Air Quality Index | National Avg. |
| Fort Green, FL | 182 | 36 | 28.0% |
| Green Mountain, IA | 182 | 39 | 22.0% |
| St. Marys, IA | 182 | 39 | 22.0% |
| Berlin, IL | 182 | 40 | 20.0% |
| Minden City, MI | 182 | 26 | 48.0% |
| Hartline, WA | 182 | 18 | 64.0% |
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