| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 12°F | 29°F | 20°F | 0.4" |
| February | 14°F | 30°F | 21°F | 1.8" |
| March | 29°F | 46°F | 36°F | 1.2" |
| April | 39°F | 62°F | 49°F | 3.6" |
| May | 50°F | 73°F | 61°F | 3.9" |
| June | 61°F | 83°F | 71°F | 2.1" |
| July | 63°F | 85°F | 74°F | 4.0" |
| August | 61°F | 82°F | 71°F | 1.6" |
| September | 53°F | 76°F | 64°F | 2.2" |
| October | 42°F | 63°F | 51°F | 3.0" |
| November | 29°F | 48°F | 38°F | 2.8" |
| December | 17°F | 32°F | 24°F | 0.7" |
| Index | Dayton | Iowa | National |
| Air quality index | 37 | 39 | 42 |
| Pollution index | 517,691 | 1,154,535 | 2,726,193 |
| Measurement | Total |
| Days measured | 214 |
| Days with good air quality | 210 |
| Days with moderate air quality | 4 |
| Days w/ poor A.Q. for sensitive groups | |
| Days with unhealthy air quality |
| 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. |
| Otho, IA | 479 | 37 | 26.0% |
| Lehigh, IA | 398 | 37 | 26.0% |
| Pilot Mound, IA | 161 | 37 | 26.0% |
| Coalville, IA | 645 | 37 | 26.0% |
| Webster City, IA | 7,699 | 37 | 26.0% |
| Dayton, IA | 839 | 37 | 26.0% |
| City | Population | Air Quality Index | National Avg. |
| Tulelake, CA | 839 | 29 | 42.0% |
| Horseshoe Bend, ID | 839 | 36 | 28.0% |
| Brownstown, IL | 839 | 40 | 20.0% |
| Ventress, LA | 839 | 45 | 10.0% |
| Middletown, MI | 839 | 38 | 24.0% |
| Dayton, IA | 839 | 37 | 26.0% |
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