| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 14°F | 30°F | 22°F | 3.8" |
| February | 14°F | 32°F | 23°F | 3.4" |
| March | 29°F | 48°F | 37°F | 4.3" |
| April | 39°F | 62°F | 50°F | 4.5" |
| May | 50°F | 74°F | 61°F | 5.4" |
| June | 59°F | 81°F | 70°F | 6.7" |
| July | 61°F | 82°F | 71°F | 6.0" |
| August | 59°F | 81°F | 69°F | 6.4" |
| September | 51°F | 76°F | 63°F | 3.8" |
| October | 41°F | 63°F | 51°F | 7.1" |
| November | 29°F | 48°F | 38°F | 3.9" |
| December | 19°F | 34°F | 26°F | 3.6" |
| Index | Oregon | Illinois | National |
| Air quality index | 42 | 41 | 42 |
| Pollution index | 1,721,090 | 3,148,694 | 2,726,193 |
| Measurement | Total |
| Days measured | 341 |
| Days with good air quality | 240 |
| Days with moderate air quality | 100 |
| Days w/ poor A.Q. for sensitive groups | 1 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.001% |
| Benzene | 0.020% |
| Carbon Tetrachloride | 0.001% |
| Lead | 0.002% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| Byron, IL | 3,607 | 42 | 16.0% |
| Leaf River, IL | 510 | 42 | 16.0% |
| Dixon, IL | 15,544 | 42 | 16.0% |
| Nelson, IL | 132 | 42 | 16.0% |
| Ashton, IL | 827 | 42 | 16.0% |
| Oregon, IL | 3,747 | 42 | 16.0% |
| City | Population | Air Quality Index | National Avg. |
| Bishop, CA | 3,747 | 47 | 6.0% |
| Norwood Young America, MN | 3,746 | 46 | 8.0% |
| Fordyce, AR | 3,748 | 32 | 36.0% |
| McGehee, AR | 3,748 | 43 | 14.0% |
| St. Charles, MN | 3,749 | 15 | 70.0% |
| Oregon, IL | 3,747 | 42 | 16.0% |
Here are the best places to live in Illinois
Safest Cities In The US
Check out the 10 most dangerous cities in Illinois
These are the largest cities in Illinois