| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 24°F | 45°F | 33°F | 0.9" |
| February | 24°F | 50°F | 35°F | 0.4" |
| March | 25°F | 55°F | 39°F | 0.6" |
| April | 29°F | 60°F | 44°F | 1.0" |
| May | 37°F | 69°F | 53°F | 0.9" |
| June | 41°F | 76°F | 59°F | 0.9" |
| July | 47°F | 90°F | 70°F | 0.1" |
| August | 45°F | 87°F | 67°F | 0.9" |
| September | 37°F | 79°F | 58°F | 0.3" |
| October | 32°F | 64°F | 46°F | 0.9" |
| November | 28°F | 52°F | 39°F | 0.9" |
| December | 19°F | 41°F | 30°F | 0.9" |
| Index | Sisters | Oregon | National |
| Air quality index | 20 | 32 | 42 |
| Pollution index | 77,038 | 7,156,356 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 341 |
| Days with moderate air quality | 19 |
| Days w/ poor A.Q. for sensitive groups | 4 |
| Days with unhealthy air quality | 1 |
| Pollutant | Total |
| Arsenic | 0.000% |
| Benzene | 0.002% |
| Carbon Tetrachloride | 0.000% |
| Lead | 0.001% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| Tumalo, OR | 407 | 20 | 60.0% |
| Eagle Crest, OR | 2,857 | 20 | 60.0% |
| Black Butte Ranch, OR | 212 | 20 | 60.0% |
| Camp Sherman, OR | 327 | 20 | 60.0% |
| Sisters, OR | 2,709 | 20 | 60.0% |
| City | Population | Air Quality Index | National Avg. |
| East Dublin, GA | 2,709 | 38 | 24.0% |
| Prince Frederick, MD | 2,709 | 41 | 18.0% |
| Concordia, MO | 2,709 | 47 | 6.0% |
| Durant, MS | 2,709 | 33 | 34.0% |
| Victor, NY | 2,709 | 37 | 26.0% |
| Sisters, OR | 2,709 | 20 | 60.0% |
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