| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 12°F | 30°F | 21°F | 0.8" |
| February | 14°F | 34°F | 23°F | 1.0" |
| March | 28°F | 49°F | 37°F | 2.2" |
| April | 39°F | 63°F | 49°F | 4.1" |
| May | 49°F | 73°F | 60°F | 5.2" |
| June | 60°F | 83°F | 71°F | 7.1" |
| July | 64°F | 86°F | 75°F | 4.2" |
| August | 62°F | 83°F | 71°F | 5.5" |
| September | 53°F | 77°F | 63°F | 2.8" |
| October | 41°F | 64°F | 51°F | 4.0" |
| November | 28°F | 49°F | 38°F | 3.7" |
| December | 16°F | 33°F | 24°F | 2.5" |
| Index | Alton | Iowa | National |
| Air quality index | 35 | 39 | 42 |
| Pollution index | 890,079 | 1,154,535 | 2,726,193 |
| Measurement | Total |
| Days measured | 364 |
| Days with good air quality | 322 |
| Days with moderate air quality | 42 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.000% |
| Benzene | 0.010% |
| Carbon Tetrachloride | 0.002% |
| Lead | 0.004% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| Maurice, IA | 295 | 35 | 30.0% |
| Struble, IA | 95 | 35 | 30.0% |
| Brunsville, IA | 140 | 35 | 30.0% |
| Orange City, IA | 6,158 | 35 | 30.0% |
| Archer, IA | 116 | 35 | 30.0% |
| Alton, IA | 1,534 | 35 | 30.0% |
| City | Population | Air Quality Index | National Avg. |
| London, CA | 1,534 | 66 | 32.0% |
| Wolcott, NY | 1,534 | 37 | 26.0% |
| Falling Water, TN | 1,534 | 46 | 8.0% |
| Hughes Springs, TX | 1,534 | 37 | 26.0% |
| Upper Island Cove, NL | 1,534 | n/a | |
| Alton, IA | 1,534 | 35 | 30.0% |
Here are the best places to live in Iowa
These are the 10 cheapest cities in Iowa
Most Dangerous Cities In The US
See the best places to live in Alton