| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 25°F | 42°F | 33°F | 4.6" |
| February | 27°F | 45°F | 35°F | 2.4" |
| March | 39°F | 58°F | 48°F | 3.7" |
| April | 48°F | 69°F | 58°F | 6.6" |
| May | 57°F | 77°F | 66°F | 10.0" |
| June | 66°F | 86°F | 76°F | 8.8" |
| July | 69°F | 88°F | 78°F | 6.8" |
| August | 67°F | 87°F | 76°F | 10.7" |
| September | 59°F | 81°F | 69°F | 7.4" |
| October | 48°F | 70°F | 58°F | 9.0" |
| November | 38°F | 57°F | 47°F | 6.5" |
| December | 30°F | 45°F | 37°F | 7.7" |
| Index | Sparta | Illinois | National |
| Air quality index | 54 | 41 | 42 |
| Pollution index | 1,232,920 | 3,148,694 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 134 |
| Days with moderate air quality | 221 |
| Days w/ poor A.Q. for sensitive groups | 8 |
| Days with unhealthy air quality | 2 |
| Pollutant | Total |
| Arsenic | 0.170% |
| Benzene | 0.030% |
| Carbon Tetrachloride | 0.000% |
| Lead | 0.010% |
| Mercury | 0.290% |
| City | Population | Air Quality Index | National Avg. |
| Steeleville, IL | 1,870 | 43 | 14.0% |
| Oakdale, IL | 291 | 43 | 14.0% |
| Willisville, IL | 596 | 43 | 14.0% |
| Cutler, IL | 429 | 43 | 14.0% |
| Coulterville, IL | 881 | 43 | 14.0% |
| Sparta, IL | 4,302 | 54 | 8.0% |
| City | Population | Air Quality Index | National Avg. |
| Golden Triangle, NJ | 4,302 | 51 | 2.0% |
| Montréal-Est, QC | 4,302 | n/a | |
| Madeira Beach, FL | 4,303 | 43 | 14.0% |
| Grayson, GA | 4,303 | 52 | 4.0% |
| Mather, CA | 4,304 | 52 | 4.0% |
| Sparta, IL | 4,302 | 54 | 8.0% |
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