| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 20°F | 39°F | 29°F | 3.5" |
| February | 21°F | 42°F | 31°F | 2.6" |
| March | 32°F | 55°F | 43°F | 4.0" |
| April | 42°F | 68°F | 55°F | 5.3" |
| May | 52°F | 76°F | 64°F | 4.8" |
| June | 62°F | 85°F | 73°F | 5.7" |
| July | 65°F | 87°F | 76°F | 4.9" |
| August | 65°F | 87°F | 75°F | 3.3" |
| September | 57°F | 81°F | 68°F | 3.4" |
| October | 45°F | 68°F | 56°F | 3.2" |
| November | 33°F | 55°F | 44°F | 3.3" |
| December | 25°F | 42°F | 33°F | 4.1" |
| Index | Southport | Indiana | National |
| Air quality index | 54 | 56 | 42 |
| Pollution index | 2,395,300 | 2,719,453 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 148 |
| Days with moderate air quality | 212 |
| Days w/ poor A.Q. for sensitive groups | 5 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.003% |
| Benzene | 0.040% |
| Carbon Tetrachloride | 0.010% |
| Lead | 0.010% |
| Mercury | 0.001% |
| City | Population | Air Quality Index | National Avg. |
| Fairland, IN | 662 | 54 | 8.0% |
| New Whiteland, IN | 6,178 | 54 | 8.0% |
| Plainfield, IN | 34,224 | 54 | 8.0% |
| Spring Lake, IN | 253 | 54 | 8.0% |
| Wynnedale, IN | 196 | 54 | 8.0% |
| Southport, IN | 1,879 | 54 | 8.0% |
| City | Population | Air Quality Index | National Avg. |
| Kersey, CO | 1,879 | 45 | 10.0% |
| Freeport, ME | 1,879 | 40 | 20.0% |
| Addison, NY | 1,879 | 35 | 30.0% |
| Ellaville, GA | 1,880 | 39 | 22.0% |
| Durant, IA | 1,878 | 32 | 36.0% |
| Southport, IN | 1,879 | 54 | 8.0% |
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