| 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 | Harrisburg | Oregon | National |
| Air quality index | 38 | 32 | 42 |
| Pollution index | 3,182,180 | 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 | 0.040% |
| Carbon Tetrachloride | 0.030% |
| Lead | 0.190% |
| Mercury | 0.110% |
| City | Population | Air Quality Index | National Avg. |
| Monroe, OR | 643 | 17 | 66.0% |
| Alpine, OR | 215 | 17 | 66.0% |
| Peoria, OR | 216 | 17 | 66.0% |
| Bellfountain, OR | 8 | 17 | 66.0% |
| Halsey, OR | 1,139 | 17 | 66.0% |
| Harrisburg, OR | 3,852 | 38 | 24.0% |
| City | Population | Air Quality Index | National Avg. |
| Lake Park, NC | 3,851 | 49 | 2.0% |
| Grape Creek, TX | 3,851 | 28 | 44.0% |
| Dumas, AR | 3,850 | 43 | 14.0% |
| Harbour Heights, FL | 3,850 | 36 | 28.0% |
| Morrison, IL | 3,850 | 42 | 16.0% |
| Harrisburg, OR | 3,852 | 38 | 24.0% |
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