| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 25°F | 41°F | 32°F | 3.3" |
| February | 27°F | 43°F | 34°F | 2.1" |
| March | 38°F | 57°F | 46°F | 4.7" |
| April | 48°F | 70°F | 58°F | 9.5" |
| May | 58°F | 78°F | 67°F | 4.8" |
| June | 66°F | 86°F | 75°F | 2.2" |
| July | 67°F | 87°F | 76°F | 8.0" |
| August | 65°F | 86°F | 75°F | 1.7" |
| September | 57°F | 81°F | 68°F | 5.4" |
| October | 47°F | 70°F | 57°F | 1.8" |
| November | 37°F | 56°F | 45°F | 6.7" |
| December | 30°F | 44°F | 36°F | 2.5" |
| Index | Allendale | Illinois | National |
| Air quality index | 36 | 41 | 42 |
| Pollution index | 500,004 | 3,148,694 | 2,726,193 |
| Measurement | Total |
| Days measured | 359 |
| Days with good air quality | 328 |
| Days with moderate air quality | 31 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.001% |
| Benzene | 0.020% |
| Carbon Tetrachloride | 0.000% |
| Lead | 0.000% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| Vincennes, IN | 17,091 | 36 | 28.0% |
| Keensburg, IL | 111 | 36 | 28.0% |
| Princeton, IN | 8,716 | 36 | 28.0% |
| Sumner, IL | 2,916 | 36 | 28.0% |
| St. Francisville, IL | 480 | 36 | 28.0% |
| Allendale, IL | 655 | 36 | 28.0% |
| City | Population | Air Quality Index | National Avg. |
| Queen Valley, AZ | 655 | 74 | 48.0% |
| Penney Farms, FL | 655 | 17 | 66.0% |
| Crooked Creek, GA | 655 | 38 | 24.0% |
| Hardin, MO | 655 | 47 | 6.0% |
| Mohall, ND | 655 | 34 | 32.0% |
| Allendale, IL | 655 | 36 | 28.0% |
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