| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 27°F | 45°F | 35°F | 3.7" |
| February | 29°F | 47°F | 37°F | 2.9" |
| March | 39°F | 60°F | 48°F | 4.5" |
| April | 48°F | 71°F | 59°F | 6.3" |
| May | 57°F | 79°F | 68°F | 5.7" |
| June | 66°F | 87°F | 77°F | 5.3" |
| July | 69°F | 89°F | 79°F | 5.6" |
| August | 68°F | 89°F | 78°F | 3.7" |
| September | 61°F | 83°F | 71°F | 4.6" |
| October | 48°F | 71°F | 59°F | 4.4" |
| November | 38°F | 59°F | 48°F | 3.5" |
| December | 31°F | 48°F | 39°F | 4.8" |
| Index | Thornhill | Kentucky | National |
| Air quality index | 49 | 45 | 42 |
| Pollution index | 10,162,700 | 1,369,131 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 195 |
| Days with moderate air quality | 166 |
| Days w/ poor A.Q. for sensitive groups | 4 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.010% |
| Benzene | 0.060% |
| Carbon Tetrachloride | 0.010% |
| Lead | 0.050% |
| Mercury | 0.140% |
| City | Population | Air Quality Index | National Avg. |
| Meadow Vale, KY | 791 | 49 | 2.0% |
| Plantation, KY | 928 | 49 | 2.0% |
| Ten Broeck, KY | 104 | 49 | 2.0% |
| Heritage Creek, KY | 861 | 49 | 2.0% |
| Lyndon, KY | 11,451 | 49 | 2.0% |
| Thornhill, KY | 193 | 49 | 2.0% |
| City | Population | Air Quality Index | National Avg. |
| Russian Mission, AK | 193 | 31 | 38.0% |
| Rackerby, CA | 193 | 44 | 12.0% |
| Grand River, IA | 193 | 39 | 22.0% |
| Oakford, IL | 193 | 40 | 20.0% |
| Severy, KS | 193 | 22 | 56.0% |
| Thornhill, KY | 193 | 49 | 2.0% |
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