| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 49°F | 63°F | 56°F | 3.7" |
| February | 52°F | 66°F | 58°F | 2.2" |
| March | 59°F | 72°F | 65°F | 3.2" |
| April | 66°F | 78°F | 71°F | 2.8" |
| May | 72°F | 83°F | 77°F | 2.7" |
| June | 79°F | 89°F | 83°F | 3.8" |
| July | 80°F | 90°F | 85°F | 4.0" |
| August | 80°F | 91°F | 85°F | 6.2" |
| September | 77°F | 88°F | 82°F | 5.0" |
| October | 69°F | 82°F | 75°F | 4.5" |
| November | 60°F | 73°F | 66°F | 3.0" |
| December | 52°F | 65°F | 58°F | 4.2" |
| Index | San Leon | Texas | National |
| Air quality index | 52 | 52 | 42 |
| Pollution index | 8,978,990 | 2,009,300 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 171 |
| Days with moderate air quality | 163 |
| Days w/ poor A.Q. for sensitive groups | 26 |
| Days with unhealthy air quality | 4 |
| Pollutant | Total |
| Arsenic | 0.020% |
| Benzene | 0.070% |
| Carbon Tetrachloride | 0.150% |
| Lead | 0.040% |
| Mercury | 0.050% |
| City | Population | Air Quality Index | National Avg. |
| El Lago, TX | 2,805 | 52 | 4.0% |
| Seabrook, TX | 13,849 | 52 | 4.0% |
| Bacliff, TX | 11,513 | 52 | 4.0% |
| Hitchcock, TX | 7,831 | 52 | 4.0% |
| Santa Fe, TX | 13,326 | 52 | 4.0% |
| San Leon, TX | 5,439 | 52 | 4.0% |
| City | Population | Air Quality Index | National Avg. |
| Cottleville, MO | 5,439 | 54 | 8.0% |
| Eagleville, PA | 5,439 | 51 | 2.0% |
| Carver, MN | 5,438 | 46 | 8.0% |
| L'Épiphanie, QC | 5,436 | n/a | |
| Cottonwood, CA | 5,435 | 42 | 16.0% |
| San Leon, TX | 5,439 | 52 | 4.0% |
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