| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 41°F | 66°F | 52°F | 6.1" |
| February | 45°F | 70°F | 56°F | 4.0" |
| March | 51°F | 78°F | 63°F | 2.6" |
| April | 59°F | 85°F | 71°F | 10.9" |
| May | 67°F | 90°F | 77°F | 8.6" |
| June | 73°F | 96°F | 83°F | 3.0" |
| July | 74°F | 96°F | 84°F | 8.2" |
| August | 74°F | 99°F | 86°F | 2.3" |
| September | 68°F | 91°F | 78°F | 10.3" |
| October | 58°F | 83°F | 70°F | 7.4" |
| November | 50°F | 75°F | 61°F | 5.9" |
| December | 42°F | 66°F | 52°F | 2.1" |
| Index | Castroville | Texas | National |
| Air quality index | 49 | 52 | 42 |
| Pollution index | 24,182,700 | 2,009,300 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 196 |
| Days with moderate air quality | 163 |
| Days w/ poor A.Q. for sensitive groups | 5 |
| Days with unhealthy air quality | 1 |
| Pollutant | Total |
| Arsenic | 0.310% |
| Benzene | 0.310% |
| Carbon Tetrachloride | 0.080% |
| Lead | 0.140% |
| Mercury | 0.230% |
| City | Population | Air Quality Index | National Avg. |
| Macdona, TX | 258 | 49 | 2.0% |
| Lytle, TX | 2,429 | 49 | 2.0% |
| Helotes, TX | 9,525 | 49 | 2.0% |
| Natalia, TX | 1,059 | 49 | 2.0% |
| Devine, TX | 4,829 | 49 | 2.0% |
| Castroville, TX | 3,097 | 49 | 2.0% |
| City | Population | Air Quality Index | National Avg. |
| Wolfdale, PA | 3,097 | 46 | 8.0% |
| Dover, FL | 3,098 | 43 | 14.0% |
| Olney, TX | 3,098 | 26 | 48.0% |
| Graymoor-Devondale, KY | 3,095 | 49 | 2.0% |
| Erlands Point-Kitsap Lake, WA | 3,095 | 18 | 64.0% |
| Castroville, TX | 3,097 | 49 | 2.0% |
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