| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 38°F | 60°F | 47°F | 2.6" |
| February | 35°F | 59°F | 45°F | 4.9" |
| March | 43°F | 70°F | 54°F | 6.6" |
| April | 49°F | 76°F | 61°F | 4.9" |
| May | 58°F | 81°F | 68°F | 1.8" |
| June | 69°F | 88°F | 76°F | 9.3" |
| July | 71°F | 90°F | 79°F | 6.4" |
| August | 72°F | 94°F | 81°F | 4.9" |
| September | 66°F | 90°F | 76°F | 1.6" |
| October | 56°F | 80°F | 66°F | 9.2" |
| November | 42°F | 69°F | 54°F | 2.1" |
| December | 37°F | 61°F | 47°F | 9.8" |
| Index | Hartsville | South Carolina | National |
| Air quality index | 40 | 37 | 42 |
| Pollution index | 1,817,360 | 3,620,438 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 288 |
| Days with moderate air quality | 77 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.010% |
| Benzene | 0.020% |
| Carbon Tetrachloride | 0.002% |
| Lead | 0.020% |
| Mercury | 0.001% |
| City | Population | Air Quality Index | National Avg. |
| Patrick, SC | 323 | 40 | 20.0% |
| Society Hill, SC | 484 | 40 | 20.0% |
| Lamar, SC | 1,123 | 40 | 20.0% |
| Bishopville, SC | 3,043 | 40 | 20.0% |
| Lydia, SC | 419 | 40 | 20.0% |
| Hartsville, SC | 7,559 | 40 | 20.0% |
| City | Population | Air Quality Index | National Avg. |
| Corbin, KY | 7,558 | 40 | 20.0% |
| Middletown CDP, PA | 7,558 | 44 | 12.0% |
| Chibougamau, QC | 7,561 | n/a | |
| Jasper, TX | 7,556 | 45 | 10.0% |
| McCook, NE | 7,555 | 19 | 62.0% |
| Hartsville, SC | 7,559 | 40 | 20.0% |
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