| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 36°F | 48°F | 41°F | 7.8" |
| February | 37°F | 53°F | 44°F | 4.4" |
| March | 40°F | 58°F | 47°F | 5.7" |
| April | 41°F | 64°F | 51°F | 3.3" |
| May | 46°F | 73°F | 57°F | 3.5" |
| June | 51°F | 78°F | 62°F | 1.9" |
| July | 54°F | 86°F | 68°F | 3.3" |
| August | 54°F | 86°F | 68°F | 2.1" |
| September | 49°F | 80°F | 63°F | 3.4" |
| October | 44°F | 67°F | 54°F | 5.6" |
| November | 40°F | 55°F | 46°F | 5.4" |
| December | 35°F | 47°F | 40°F | 7.2" |
| Index | Philomath | Oregon | National |
| Air quality index | 17 | 32 | 42 |
| Pollution index | 3,182,180 | 7,156,356 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 332 |
| Days with moderate air quality | 33 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.010% |
| Benzene | 0.040% |
| Carbon Tetrachloride | 0.030% |
| Lead | 0.190% |
| Mercury | 0.110% |
| City | Population | Air Quality Index | National Avg. |
| Alsea, OR | 220 | 17 | 66.0% |
| Shedd, OR | 290 | 17 | 66.0% |
| Corvallis, OR | 58,612 | 17 | 66.0% |
| Bellfountain, OR | 8 | 17 | 66.0% |
| Kings Valley, OR | 194 | 17 | 66.0% |
| Philomath, OR | 5,143 | 17 | 66.0% |
| City | Population | Air Quality Index | National Avg. |
| Myrtletown, CA | 5,143 | 27 | 46.0% |
| Granite Shoals, TX | 5,142 | 44 | 12.0% |
| Birdsboro, PA | 5,141 | 42 | 16.0% |
| Gilmer, TX | 5,139 | 37 | 26.0% |
| Colchester, CT | 5,147 | 33 | 34.0% |
| Philomath, OR | 5,143 | 17 | 66.0% |
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