| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 14°F | 37°F | 24°F | 0.6" |
| February | 16°F | 41°F | 27°F | 0.9" |
| March | 29°F | 56°F | 41°F | 1.5" |
| April | 40°F | 67°F | 53°F | 3.8" |
| May | 50°F | 77°F | 63°F | 5.2" |
| June | 62°F | 87°F | 74°F | 4.9" |
| July | 66°F | 91°F | 78°F | 3.1" |
| August | 64°F | 88°F | 75°F | 6.1" |
| September | 55°F | 82°F | 67°F | 3.7" |
| October | 42°F | 69°F | 54°F | 3.0" |
| November | 29°F | 55°F | 41°F | 1.0" |
| December | 17°F | 39°F | 27°F | 1.7" |
| Index | Jacksonville | Iowa | National |
| Air quality index | 48 | 39 | 50 |
| Pollution index | 517,691 | 1,643,836 | 5,066,862 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 197 |
| Days with moderate air quality | 164 |
| Days w/ poor A.Q. for sensitive groups | 4 |
| Days with unhealthy air quality |
| Pollutant | Total |
| Arsenic | 0.000% |
| Benzene | 0.010% |
| Carbon Tetrachloride | 0.001% |
| Lead | 0.002% |
| Mercury | 0.000% |
| City, State | Population | Air Quality Index | National Avg. |
| Avoca, IA | 1,478 | 48 | 4% |
| Earling, IA | 443 | 48 | 4% |
| Harlan, IA | 5,008 | 48 | 4% |
| Marne, IA | 120 | 48 | 4% |
| Brayton, IA | 145 | 48 | 4% |
| Jacksonville, IA | 32 | 48 | 4% |
| City, State | Population | Air Quality Index | National Avg. |
| Nenzel, NE | 32 | 43 | 14% |
| Alice, ND | 32 | 35 | 30% |
| Union Hill, IL | 32 | 1 | 98% |
| Zion, OK | 32 | 36 | 28% |
| Clam Lake, WI | 32 | 37 | 26% |
| Jacksonville, IA | 32 | 48 | 4% |