| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 20°F | 38°F | 29°F | 2.1" |
| February | 22°F | 41°F | 31°F | 1.9" |
| March | 34°F | 56°F | 44°F | 2.9" |
| April | 44°F | 68°F | 56°F | 4.3" |
| May | 54°F | 77°F | 65°F | 4.5" |
| June | 64°F | 86°F | 74°F | 5.5" |
| July | 66°F | 88°F | 77°F | 4.3" |
| August | 64°F | 86°F | 75°F | 3.2" |
| September | 57°F | 81°F | 68°F | 3.7" |
| October | 46°F | 69°F | 56°F | 3.7" |
| November | 36°F | 55°F | 45°F | 2.5" |
| December | 26°F | 41°F | 33°F | 2.8" |
| Index | Petersburg | Illinois | National |
| Air quality index | 40 | 41 | 50 |
| Pollution index | 400,905 | 3,347,295 | 5,066,862 |
| Measurement | Total |
| Days measured | 360 |
| Days with good air quality | 287 |
| Days with moderate air quality | 73 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.000% |
| Benzene | 0.020% |
| Carbon Tetrachloride | 0.000% |
| Lead | 0.000% |
| Mercury | 0.000% |
| City, State | Population | Air Quality Index | National Avg. |
| Pleasant Plains, IL | 864 | 40 | 20% |
| Tallula, IL | 492 | 40 | 20% |
| Greenview, IL | 844 | 40 | 20% |
| New Holland, IL | 187 | 40 | 20% |
| Oakford, IL | 298 | 40 | 20% |
| Petersburg, IL | 2,333 | 40 | 20% |
| City, State | Population | Air Quality Index | National Avg. |
| Ellinwood, KS | 2,332 | 40 | 20% |
| Freeport, FL | 2,332 | 31 | 38% |
| Rangely, CO | 2,331 | 49 | 2% |
| Kure Beach, NC | 2,335 | 34 | 32% |
| Inez, TX | 2,335 | 31 | 38% |
| Petersburg, IL | 2,333 | 40 | 20% |
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