| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 12°F | 29°F | 20°F | 0.8" |
| February | 14°F | 32°F | 23°F | 1.0" |
| March | 28°F | 48°F | 37°F | 2.1" |
| April | 39°F | 63°F | 50°F | 4.6" |
| May | 50°F | 73°F | 61°F | 3.9" |
| June | 60°F | 81°F | 70°F | 7.0" |
| July | 63°F | 84°F | 73°F | 4.8" |
| August | 61°F | 82°F | 71°F | 4.7" |
| September | 53°F | 76°F | 64°F | 4.0" |
| October | 42°F | 63°F | 52°F | 3.1" |
| November | 29°F | 49°F | 38°F | 2.1" |
| December | 17°F | 33°F | 25°F | 1.9" |
| Index | Marion | Iowa | National |
| Air quality index | 39 | 39 | 50 |
| Pollution index | 5,075,380 | 1,643,836 | 5,066,862 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 287 |
| Days with moderate air quality | 78 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.070% |
| Benzene | 0.050% |
| Carbon Tetrachloride | 2.000% |
| Lead | 0.040% |
| Mercury | 0.100% |
| City, State | Population | Air Quality Index | National Avg. |
| Center Point, IA | 2,507 | 39 | 22% |
| Lisbon, IA | 1,908 | 39 | 22% |
| Shellsburg, IA | 1,097 | 39 | 22% |
| Martelle, IA | 266 | 39 | 22% |
| Stone City, IA | 288 | 39 | 22% |
| Marion, IA | 37,198 | 39 | 22% |
| City, State | Population | Air Quality Index | National Avg. |
| Mechanicsville, VA | 37,201 | 44 | 12% |
| Addison, IL | 37,192 | 55 | 10% |
| East Meadow, NY | 37,228 | 51 | 2% |
| Lincoln Park, MI | 37,155 | 56 | 12% |
| Calumet City, IL | 37,112 | 55 | 10% |
| Marion, IA | 37,198 | 39 | 22% |
Here are the best places to live in Iowa
Top 10 best public schools in Marion
These are the 10 most affordable cities in Iowa
10 Best cities in Iowa for employment