| 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 | Brownsville | Oregon | National |
| Air quality index | 28 | 32 | 42 |
| Pollution index | 77,038 | 7,156,356 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 280 |
| Days with moderate air quality | 83 |
| Days w/ poor A.Q. for sensitive groups | 2 |
| Days with unhealthy air quality | 0 |
| 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. |
| Halsey, OR | 1,139 | 17 | 66.0% |
| Peoria, OR | 216 | 17 | 66.0% |
| Corvallis, OR | 58,612 | 17 | 66.0% |
| Shedd, OR | 290 | 17 | 66.0% |
| South Lebanon, OR | 903 | 28 | 44.0% |
| Brownsville, OR | 2,139 | 28 | 44.0% |
| City | Population | Air Quality Index | National Avg. |
| North Judson, IN | 2,139 | 37 | 26.0% |
| Piketon, OH | 2,139 | 14 | 72.0% |
| Little River-Academy, TX | 2,139 | 42 | 16.0% |
| Lisbon, IA | 2,138 | 39 | 22.0% |
| Mooreville, MS | 2,138 | 39 | 22.0% |
| Brownsville, OR | 2,139 | 28 | 44.0% |
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