| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 17°F | 37°F | 26°F | 1.8" |
| February | 19°F | 40°F | 29°F | 1.9" |
| March | 32°F | 55°F | 42°F | 3.1" |
| April | 42°F | 66°F | 53°F | 4.7" |
| May | 52°F | 74°F | 62°F | 4.8" |
| June | 62°F | 84°F | 72°F | 6.9" |
| July | 65°F | 87°F | 76°F | 4.3" |
| August | 63°F | 85°F | 73°F | 4.3" |
| September | 55°F | 79°F | 66°F | 4.1" |
| October | 44°F | 66°F | 54°F | 4.0" |
| November | 33°F | 54°F | 42°F | 2.6" |
| December | 22°F | 39°F | 30°F | 1.9" |
| Index | Callao | Missouri | National |
| Air quality index | 38 | 97 | 42 |
| Pollution index | 637,848 | 1,630,255 | 2,726,193 |
| Measurement | Total |
| Days measured | 245 |
| Days with good air quality | 239 |
| Days with moderate air quality | 6 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.001% |
| Benzene | 0.010% |
| Carbon Tetrachloride | 0.001% |
| Lead | 0.001% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| Bucklin, MO | 359 | 38 | 24.0% |
| Excello, MO | 29 | 38 | 24.0% |
| Macon, MO | 5,357 | 38 | 24.0% |
| Ethel, MO | 54 | 38 | 24.0% |
| Bevier, MO | 671 | 38 | 24.0% |
| Callao, MO | 319 | 38 | 24.0% |
| City | Population | Air Quality Index | National Avg. |
| Horn Hill, AL | 319 | 35 | 30.0% |
| Cash, AR | 319 | 45 | 10.0% |
| Brooker, FL | 319 | 35 | 30.0% |
| Bronwood, GA | 319 | 39 | 22.0% |
| Taylorsville, GA | 319 | 44 | 12.0% |
| Callao, MO | 319 | 38 | 24.0% |
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