| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 46°F | 66°F | 54°F | 2.8" |
| February | 50°F | 69°F | 58°F | 1.9" |
| March | 56°F | 75°F | 65°F | 2.5" |
| April | 62°F | 80°F | 71°F | 3.4" |
| May | 69°F | 85°F | 76°F | 3.4" |
| June | 74°F | 91°F | 82°F | 2.5" |
| July | 75°F | 92°F | 83°F | 2.3" |
| August | 75°F | 93°F | 83°F | 5.0" |
| September | 71°F | 89°F | 79°F | 3.1" |
| October | 62°F | 84°F | 72°F | 2.3" |
| November | 55°F | 75°F | 64°F | 2.3" |
| December | 49°F | 68°F | 57°F | 2.2" |
| Index | Sweeny | Texas | National |
| Air quality index | 52 | 52 | 42 |
| Pollution index | 6,628,750 | 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 | 0.080% |
| Carbon Tetrachloride | 0.660% |
| Lead | 0.060% |
| Mercury | 0.030% |
| City | Population | Air Quality Index | National Avg. |
| Brazoria, TX | 3,077 | 52 | 4.0% |
| Van Vleck, TX | 1,293 | 52 | 4.0% |
| Holiday Lakes, TX | 986 | 52 | 4.0% |
| West Columbia, TX | 3,871 | 52 | 4.0% |
| Boling, TX | 1,104 | 52 | 4.0% |
| Sweeny, TX | 3,666 | 52 | 4.0% |
| City | Population | Air Quality Index | National Avg. |
| Milan, NM | 3,665 | 17 | 66.0% |
| Inman, SC | 3,665 | 44 | 12.0% |
| Ballinger, TX | 3,665 | 33 | 34.0% |
| Woodlands, MB | 3,665 | n/a | |
| Northfield, OH | 3,667 | 50 | = 100 |
| Sweeny, TX | 3,666 | 52 | 4.0% |
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