| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 19°F | 35°F | 27°F | 3.7" |
| February | 20°F | 37°F | 28°F | 2.9" |
| March | 33°F | 52°F | 41°F | 4.7" |
| April | 42°F | 66°F | 53°F | 5.6" |
| May | 54°F | 76°F | 64°F | 6.5" |
| June | 63°F | 84°F | 73°F | 7.6" |
| July | 65°F | 85°F | 75°F | 10.4" |
| August | 62°F | 83°F | 72°F | 7.8" |
| September | 55°F | 79°F | 66°F | 7.6" |
| October | 44°F | 66°F | 54°F | 4.3" |
| November | 34°F | 53°F | 42°F | 5.5" |
| December | 24°F | 39°F | 31°F | 3.5" |
| Index | Ransom | Illinois | National |
| Air quality index | 0 | 41 | 42 |
| Pollution index | 1,736,930 | 3,148,694 | 2,726,193 |
| Measurement | Total |
| Days measured | 335 |
| Days with good air quality | 334 |
| Days with moderate air quality | 1 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.004% |
| Benzene | 0.040% |
| Carbon Tetrachloride | 0.000% |
| Lead | 0.001% |
| Mercury | 0.001% |
| City | Population | Air Quality Index | National Avg. |
| Cornell, IL | 428 | 0 | 100.0% |
| Kangley, IL | 244 | 0 | 100.0% |
| Seneca, IL | 2,534 | 0 | 100.0% |
| Morris, IL | 14,420 | 0 | 100.0% |
| Long Point, IL | 250 | 0 | 100.0% |
| Ransom, IL | 355 | 0 | 100.0% |
| City | Population | Air Quality Index | National Avg. |
| Rockford Bay, ID | 355 | 43 | 14.0% |
| Latham, IL | 355 | 44 | 12.0% |
| Gridley, KS | 355 | 22 | 56.0% |
| Spottsville, KY | 355 | 45 | 10.0% |
| Branch, LA | 355 | 41 | 18.0% |
| Ransom, IL | 355 | 0 | 100.0% |
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