| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 13°F | 29°F | 21°F | 1.4" |
| February | 14°F | 32°F | 22°F | 1.1" |
| March | 28°F | 47°F | 37°F | 2.8" |
| April | 39°F | 61°F | 49°F | 4.6" |
| May | 50°F | 72°F | 60°F | 5.1" |
| June | 60°F | 80°F | 69°F | 8.0" |
| July | 63°F | 84°F | 73°F | 5.2" |
| August | 61°F | 82°F | 71°F | 5.1" |
| September | 54°F | 76°F | 63°F | 4.2" |
| October | 43°F | 63°F | 52°F | 4.1" |
| November | 31°F | 49°F | 39°F | 3.2" |
| December | 18°F | 33°F | 26°F | 3.2" |
| Index | Clayton | Iowa | National |
| Air quality index | 29 | 39 | 42 |
| Pollution index | 1,904,120 | 1,154,535 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 304 |
| Days with moderate air quality | 60 |
| Days w/ poor A.Q. for sensitive groups | 1 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.040% |
| Benzene | 0.020% |
| Carbon Tetrachloride | 0.001% |
| Lead | 0.010% |
| Mercury | 0.050% |
| City | Population | Air Quality Index | National Avg. |
| Garnavillo, IA | 815 | 29 | 42.0% |
| Monona, IA | 1,639 | 29 | 42.0% |
| Farmersburg, IA | 371 | 29 | 42.0% |
| Bloomington, WI | 735 | 29 | 42.0% |
| Elkader, IA | 1,362 | 29 | 42.0% |
| Clayton, IA | 68 | 29 | 42.0% |
| City | Population | Air Quality Index | National Avg. |
| Ekwok, AK | 68 | 31 | 38.0% |
| Union Grove, AL | 68 | 44 | 12.0% |
| Anthonyville, AR | 68 | 45 | 10.0% |
| Marie, AR | 68 | 45 | 10.0% |
| Keddie, CA | 68 | 46 | 8.0% |
| Clayton, IA | 68 | 29 | 42.0% |
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