| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 14°F | 30°F | 21°F | 1.4" |
| February | 17°F | 33°F | 24°F | 2.7" |
| March | 31°F | 50°F | 39°F | 3.7" |
| April | 40°F | 63°F | 50°F | 7.2" |
| May | 52°F | 74°F | 62°F | 7.7" |
| June | 62°F | 82°F | 72°F | 7.8" |
| July | 65°F | 85°F | 74°F | 7.6" |
| August | 63°F | 82°F | 72°F | 7.4" |
| September | 54°F | 77°F | 64°F | 7.1" |
| October | 43°F | 64°F | 53°F | 6.9" |
| November | 32°F | 50°F | 40°F | 3.7" |
| December | 20°F | 35°F | 27°F | 5.3" |
| Index | Sully | Iowa | National |
| Air quality index | 39 | 39 | 42 |
| Pollution index | 3,955,060 | 1,154,535 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 306 |
| Days with moderate air quality | 59 |
| 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 | 0.002% |
| Lead | 0.002% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| Newton, IA | 15,160 | 39 | 22.0% |
| Lynnville, IA | 541 | 39 | 22.0% |
| Searsboro, IA | 134 | 39 | 22.0% |
| Grinnell, IA | 9,069 | 39 | 22.0% |
| Monroe, IA | 1,810 | 39 | 22.0% |
| Sully, IA | 962 | 39 | 22.0% |
| City | Population | Air Quality Index | National Avg. |
| Anacoco, LA | 962 | 30 | 40.0% |
| Cotton Valley, LA | 962 | 39 | 22.0% |
| Alanson, MI | 962 | 36 | 28.0% |
| Clarkfield, MN | 962 | 32 | 36.0% |
| Schurz, NV | 962 | 41 | 18.0% |
| Sully, IA | 962 | 39 | 22.0% |
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