| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 21°F | 39°F | 29°F | 3.5" |
| February | 23°F | 41°F | 31°F | 3.2" |
| March | 36°F | 56°F | 44°F | 3.6" |
| April | 46°F | 68°F | 56°F | 7.4" |
| May | 56°F | 76°F | 65°F | 7.6" |
| June | 64°F | 84°F | 74°F | 10.4" |
| July | 67°F | 87°F | 76°F | 8.6" |
| August | 65°F | 87°F | 75°F | 6.1" |
| September | 58°F | 81°F | 68°F | 8.5" |
| October | 46°F | 68°F | 56°F | 5.6" |
| November | 36°F | 55°F | 45°F | 5.5" |
| December | 27°F | 42°F | 33°F | 6.1" |
| Index | Griggsville | Illinois | National |
| Air quality index | 41 | 41 | 42 |
| Pollution index | 222,633 | 3,148,694 | 2,726,193 |
| Measurement | Total |
| Days measured | 241 |
| Days with good air quality | 208 |
| Days with moderate air quality | 33 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.003% |
| Benzene | 0.010% |
| Carbon Tetrachloride | 0.000% |
| Lead | 0.002% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| Glasgow, IL | 93 | 40 | 20.0% |
| Exeter, IL | 72 | 40 | 20.0% |
| Winchester, IL | 1,717 | 40 | 20.0% |
| El Dara, IL | 88 | 41 | 18.0% |
| New Salem, IL | 207 | 41 | 18.0% |
| Griggsville, IL | 1,454 | 41 | 18.0% |
| City | Population | Air Quality Index | National Avg. |
| Noank, CT | 1,454 | 37 | 26.0% |
| Long Creek, IL | 1,454 | 44 | 12.0% |
| Babbitt, MN | 1,454 | 35 | 30.0% |
| Goodman, MO | 1,454 | 37 | 26.0% |
| Head of the Harbor, NY | 1,454 | 43 | 14.0% |
| Griggsville, IL | 1,454 | 41 | 18.0% |
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