| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 8°F | 27°F | 17°F | 0.3" |
| February | 10°F | 30°F | 19°F | 0.5" |
| March | 26°F | 46°F | 34°F | 1.2" |
| April | 36°F | 61°F | 47°F | 2.9" |
| May | 48°F | 73°F | 59°F | 4.0" |
| June | 58°F | 82°F | 70°F | 5.0" |
| July | 62°F | 86°F | 74°F | 3.2" |
| August | 59°F | 82°F | 70°F | 4.3" |
| September | 51°F | 77°F | 63°F | 2.9" |
| October | 39°F | 63°F | 49°F | 2.3" |
| November | 25°F | 48°F | 36°F | 0.9" |
| December | 12°F | 30°F | 21°F | 0.8" |
| Index | Royal | Iowa | National |
| Air quality index | 35 | 39 | 42 |
| Pollution index | 769,697 | 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 | 0.001% |
| Lead | 0.002% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| Everly, IA | 595 | 35 | 30.0% |
| Gillett Grove, IA | 26 | 35 | 30.0% |
| Linn Grove, IA | 177 | 35 | 30.0% |
| Calumet, IA | 159 | 35 | 30.0% |
| Fostoria, IA | 180 | 35 | 30.0% |
| Royal, IA | 505 | 35 | 30.0% |
| City | Population | Air Quality Index | National Avg. |
| Galena, AK | 505 | 38 | 24.0% |
| Beulah Valley, CO | 505 | 20 | 60.0% |
| Sumner, GA | 505 | 40 | 20.0% |
| Cisne, IL | 505 | 43 | 14.0% |
| West College Corner, IN | 505 | 6 | 88.0% |
| Royal, IA | 505 | 35 | 30.0% |
Here are the best places to live in Iowa
These are the 10 cheapest cities in Iowa
Most Dangerous States In The US
Check out the 10 safest cities in Iowa