| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 18°F | 34°F | 26°F | 3.3" |
| February | 19°F | 35°F | 26°F | 3.0" |
| March | 32°F | 51°F | 40°F | 4.3" |
| April | 42°F | 64°F | 52°F | 7.2" |
| May | 53°F | 75°F | 63°F | 8.0" |
| June | 62°F | 83°F | 72°F | 7.5" |
| July | 66°F | 85°F | 75°F | 7.1" |
| August | 64°F | 83°F | 73°F | 8.2" |
| September | 56°F | 78°F | 66°F | 6.3" |
| October | 45°F | 65°F | 54°F | 6.6" |
| November | 34°F | 51°F | 42°F | 4.3" |
| December | 23°F | 37°F | 30°F | 3.5" |
| Index | LaSalle | Illinois | National |
| Air quality index | 0 | 41 | 42 |
| Pollution index | 1,874,490 | 3,148,694 | 2,726,193 |
| Measurement | Total |
| Days measured | 335 |
| Days with good air quality | 334 |
| Days with moderate air quality | 1 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.002% |
| Benzene | 0.030% |
| Carbon Tetrachloride | 0.010% |
| Lead | 0.010% |
| Mercury | 0.010% |
| City | Population | Air Quality Index | National Avg. |
| Troy Grove, IL | 210 | 0 | 100.0% |
| Dalzell, IL | 628 | 0 | 100.0% |
| Mark, IL | 534 | 0 | 100.0% |
| Hollowayville, IL | 57 | 0 | 100.0% |
| Peru, IL | 9,777 | 0 | 100.0% |
| LaSalle, IL | 9,086 | 0 | 100.0% |
| City | Population | Air Quality Index | National Avg. |
| Burlington, WA | 9,085 | 24 | 52.0% |
| Rochelle, IL | 9,083 | 42 | 16.0% |
| Tsinstikeptum 9, BC | 9,090 | n/a | |
| Boulder Hill, IL | 9,081 | 55 | 10.0% |
| Innsbrook, VA | 9,081 | 44 | 12.0% |
| LaSalle, IL | 9,086 | 0 | 100.0% |
Here are the best places to live in Illinois
See the best places to live in LaSalle
Check out the 10 most dangerous cities in Illinois
Most Dangerous Cities In The US