| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 44°F | 66°F | 54°F | 0.3" |
| February | 48°F | 71°F | 59°F | 8.8" |
| March | 56°F | 75°F | 65°F | 5.9" |
| April | 60°F | 79°F | 69°F | 1.3" |
| May | 64°F | 82°F | 73°F | 10.3" |
| June | 71°F | 89°F | 79°F | 10.1" |
| July | 73°F | 93°F | 82°F | 9.8" |
| August | 71°F | 92°F | 80°F | 24.8" |
| September | 69°F | 89°F | 77°F | 5.3" |
| October | 58°F | 83°F | 70°F | 6.9" |
| November | 51°F | 75°F | 62°F | 1.0" |
| December | 46°F | 68°F | 56°F | 4.6" |
| Index | Mermentau | Louisiana | National |
| Air quality index | 41 | 106 | 42 |
| Pollution index | 1,171,580 | 2,526,475 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 280 |
| Days with moderate air quality | 85 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.000% |
| Benzene | 0.020% |
| Carbon Tetrachloride | 0.002% |
| Lead | 0.004% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| Egan, LA | 1,002 | 41 | 18.0% |
| Iota, LA | 1,752 | 41 | 18.0% |
| Estherwood, LA | 676 | 41 | 18.0% |
| Morse, LA | 1,239 | 41 | 18.0% |
| Gueydan, LA | 1,184 | 41 | 18.0% |
| Mermentau, LA | 616 | 41 | 18.0% |
| City | Population | Air Quality Index | National Avg. |
| Shipman, IL | 616 | 54 | 8.0% |
| Killona, LA | 616 | 41 | 18.0% |
| Parma, MO | 616 | 26 | 48.0% |
| Sherman, MS | 616 | 39 | 22.0% |
| Newton Grove, NC | 616 | 40 | 20.0% |
| Mermentau, LA | 616 | 41 | 18.0% |
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