| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 33°F | 49°F | 40°F | 4.9" |
| February | 34°F | 53°F | 43°F | 4.3" |
| March | 37°F | 58°F | 47°F | 5.0" |
| April | 38°F | 63°F | 50°F | 2.6" |
| May | 43°F | 70°F | 56°F | 2.2" |
| June | 47°F | 76°F | 61°F | 1.2" |
| July | 51°F | 86°F | 68°F | 0.4" |
| August | 51°F | 87°F | 68°F | 0.3" |
| September | 47°F | 80°F | 62°F | 1.2" |
| October | 42°F | 66°F | 53°F | 3.6" |
| November | 37°F | 55°F | 45°F | 6.0" |
| December | 32°F | 48°F | 39°F | 6.7" |
| Index | Cottage Grove | Oregon | National |
| Air quality index | 38 | 32 | 42 |
| Pollution index | 3,310,060 | 7,156,356 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 254 |
| Days with moderate air quality | 103 |
| Days w/ poor A.Q. for sensitive groups | 8 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.010% |
| Benzene | 0.050% |
| Carbon Tetrachloride | 0.020% |
| Lead | 0.020% |
| Mercury | 0.005% |
| City | Population | Air Quality Index | National Avg. |
| Yoncalla, OR | 1,166 | 24 | 52.0% |
| Drain, OR | 955 | 38 | 24.0% |
| Lowell, OR | 1,027 | 38 | 24.0% |
| Creswell, OR | 5,445 | 38 | 24.0% |
| Cottage Grove, OR | 10,302 | 38 | 24.0% |
| City | Population | Air Quality Index | National Avg. |
| Melvindale, MI | 10,300 | 56 | 12.0% |
| Forest Acres, SC | 10,300 | 43 | 14.0% |
| Bluffton, IN | 10,298 | 31 | 38.0% |
| Nanticoke, PA | 10,296 | 38 | 24.0% |
| Amelia, OH | 10,308 | 54 | 8.0% |
| Cottage Grove, OR | 10,302 | 38 | 24.0% |
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