| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 33°F | 52°F | 41°F | 9.0" |
| February | 34°F | 54°F | 43°F | 6.2" |
| March | 43°F | 65°F | 52°F | 4.9" |
| April | 50°F | 74°F | 61°F | 7.0" |
| May | 58°F | 79°F | 67°F | 4.2" |
| June | 65°F | 88°F | 76°F | 4.9" |
| July | 68°F | 90°F | 78°F | 7.6" |
| August | 68°F | 89°F | 77°F | 5.8" |
| September | 62°F | 83°F | 71°F | 3.7" |
| October | 50°F | 73°F | 60°F | 6.2" |
| November | 40°F | 63°F | 50°F | 5.1" |
| December | 37°F | 55°F | 45°F | 7.9" |
| Index | Hartselle | Alabama | National |
| Air quality index | 41 | 37 | 42 |
| Pollution index | 6,960,530 | 3,012,339 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 306 |
| Days with moderate air quality | 59 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.010% |
| Benzene | 0.100% |
| Carbon Tetrachloride | 0.060% |
| Lead | 0.030% |
| Mercury | 0.010% |
| City | Population | Air Quality Index | National Avg. |
| Decatur, AL | 54,344 | 41 | 18.0% |
| Priceville, AL | 3,682 | 41 | 18.0% |
| Eva, AL | 538 | 41 | 18.0% |
| Somerville, AL | 653 | 41 | 18.0% |
| Hillsboro, AL | 590 | 41 | 18.0% |
| Hartselle, AL | 14,421 | 41 | 18.0% |
| City | Population | Air Quality Index | National Avg. |
| Sterling, CO | 14,421 | 45 | 10.0% |
| Villas, FL | 14,421 | 36 | 28.0% |
| Morris, IL | 14,420 | 0 | 100.0% |
| Rio Grande City, TX | 14,411 | 42 | 16.0% |
| Mont-Laurier, QC | 14,402 | n/a | |
| Hartselle, AL | 14,421 | 41 | 18.0% |
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