| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 12°F | 27°F | 19°F | 0.7" |
| February | 13°F | 29°F | 21°F | 0.7" |
| March | 29°F | 45°F | 36°F | 1.7" |
| April | 39°F | 60°F | 48°F | 2.8" |
| May | 50°F | 71°F | 60°F | 2.4" |
| June | 60°F | 80°F | 70°F | 5.1" |
| July | 62°F | 82°F | 72°F | 2.5" |
| August | 60°F | 79°F | 69°F | 2.3" |
| September | 53°F | 75°F | 63°F | 3.0" |
| October | 42°F | 61°F | 50°F | 2.8" |
| November | 29°F | 47°F | 37°F | 1.1" |
| December | 17°F | 31°F | 24°F | 1.8" |
| Index | Oelwein | Iowa | National |
| Air quality index | 39 | 39 | 42 |
| Pollution index | 530,484 | 1,154,535 | 2,726,193 |
| Measurement | Total |
| Days measured | 363 |
| Days with good air quality | 286 |
| Days with moderate air quality | 77 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.000% |
| Benzene | 0.010% |
| Carbon Tetrachloride | 0.001% |
| Lead | 0.002% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| Maynard, IA | 506 | 39 | 22.0% |
| Randalia, IA | 61 | 39 | 22.0% |
| Hazleton, IA | 766 | 39 | 22.0% |
| Dunkerton, IA | 983 | 39 | 22.0% |
| Arlington, IA | 496 | 39 | 22.0% |
| Oelwein, IA | 5,896 | 39 | 22.0% |
| City | Population | Air Quality Index | National Avg. |
| Sweetwater, TN | 5,894 | 30 | 40.0% |
| Ramblewood, NJ | 5,899 | 51 | 2.0% |
| McKees Rocks, PA | 5,892 | 56 | 12.0% |
| Littlefield, TX | 5,900 | 25 | 50.0% |
| Wesley Hills, NY | 5,891 | 51 | 2.0% |
| Oelwein, IA | 5,896 | 39 | 22.0% |
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