| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 18°F | 34°F | 25°F | 2.5" |
| February | 19°F | 36°F | 27°F | 2.8" |
| March | 31°F | 50°F | 39°F | 4.5" |
| April | 41°F | 63°F | 51°F | 4.9" |
| May | 50°F | 73°F | 61°F | 4.7" |
| June | 60°F | 83°F | 71°F | 5.4" |
| July | 64°F | 85°F | 74°F | 5.7" |
| August | 62°F | 83°F | 72°F | 6.8" |
| September | 55°F | 77°F | 65°F | 5.4" |
| October | 44°F | 64°F | 53°F | 5.7" |
| November | 33°F | 51°F | 41°F | 4.9" |
| December | 23°F | 37°F | 30°F | 3.7" |
| Index | Joliet | Illinois | National |
| Air quality index | 60 | 41 | 50 |
| Pollution index | 1,558,070 | 3,347,295 | 5,066,862 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 72 |
| Days with moderate air quality | 281 |
| Days w/ poor A.Q. for sensitive groups | 11 |
| Days with unhealthy air quality | 1 |
| Pollutant | Total |
| Arsenic | 0.010% |
| Benzene | 0.010% |
| Carbon Tetrachloride | 0.070% |
| Lead | 0.090% |
| Mercury | 0.010% |
| City, State | Population | Air Quality Index | National Avg. |
| Montgomery, IL | 19,055 | 1 | 98% |
| Oswego, IL | 33,245 | 1 | 98% |
| Elwood, IL | 2,144 | 1 | 98% |
| Shorewood, IL | 16,539 | 1 | 98% |
| Wilmington village, IL | 144 | 1 | 98% |
| Joliet, IL | 147,515 | 60 | 20% |
| City, State | Population | Air Quality Index | National Avg. |
| Torrance, CA | 147,307 | 74 | 48% |
| Bridgeport, CT | 147,022 | 47 | 6% |
| Hollywood, FL | 148,114 | 41 | 18% |
| Paterson, NJ | 146,894 | 53 | 6% |
| Clarksville, TN | 146,281 | 41 | 18% |
| Joliet, IL | 147,515 | 60 | 20% |