| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 22°F | 42°F | 32°F | 3.4" |
| February | 23°F | 44°F | 33°F | 3.1" |
| March | 33°F | 57°F | 44°F | 4.6" |
| April | 43°F | 69°F | 56°F | 5.0" |
| May | 52°F | 77°F | 64°F | 4.0" |
| June | 61°F | 85°F | 73°F | 5.2" |
| July | 65°F | 87°F | 76°F | 4.0" |
| August | 64°F | 88°F | 76°F | 3.0" |
| September | 57°F | 81°F | 69°F | 4.1" |
| October | 45°F | 69°F | 57°F | 4.1" |
| November | 34°F | 57°F | 45°F | 3.5" |
| December | 27°F | 45°F | 36°F | 4.5" |
| Index | Union | Kentucky | National |
| Air quality index | 54 | 45 | 42 |
| Pollution index | 23,937,200 | 1,369,131 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 139 |
| Days with moderate air quality | 206 |
| Days w/ poor A.Q. for sensitive groups | 20 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.500% |
| Benzene | 0.180% |
| Carbon Tetrachloride | 0.110% |
| Lead | 0.250% |
| Mercury | 0.060% |
| City | Population | Air Quality Index | National Avg. |
| Walton, KY | 4,343 | 54 | 8.0% |
| Verona, KY | 1,222 | 54 | 8.0% |
| Covington, KY | 40,466 | 54 | 8.0% |
| Newport, KY | 15,045 | 54 | 8.0% |
| Villa Hills, KY | 7,475 | 54 | 8.0% |
| Union, KY | 5,988 | 54 | 8.0% |
| City | Population | Air Quality Index | National Avg. |
| Shaw Heights, CO | 5,987 | 58 | 16.0% |
| Pontiac, QC | 5,989 | n/a | |
| Maquoketa, IA | 5,990 | 42 | 16.0% |
| Charles Town, WV | 5,985 | 38 | 24.0% |
| Kodiak, AK | 5,983 | 31 | 38.0% |
| Union, KY | 5,988 | 54 | 8.0% |
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