| 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 | Rochelle | 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. |
| Lee, IL | 380 | 0 | 100.0% |
| Shabbona, IL | 937 | 0 | 100.0% |
| Amboy, IL | 2,453 | 0 | 100.0% |
| Malta, IL | 1,431 | 42 | 16.0% |
| Byron, IL | 3,607 | 42 | 16.0% |
| Rochelle, IL | 9,083 | 42 | 16.0% |
| City | Population | Air Quality Index | National Avg. |
| Boulder Hill, IL | 9,081 | 55 | 10.0% |
| Innsbrook, VA | 9,081 | 44 | 12.0% |
| Merrill, WI | 9,081 | 34 | 32.0% |
| Burlington, WA | 9,085 | 24 | 52.0% |
| LaSalle, IL | 9,086 | 0 | 100.0% |
| Rochelle, IL | 9,083 | 42 | 16.0% |
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