| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 45°F | 62°F | 52°F | 11.2" |
| February | 45°F | 61°F | 52°F | 3.4" |
| March | 46°F | 62°F | 53°F | 1.1" |
| April | 46°F | 62°F | 53°F | 20.7" |
| May | 49°F | 62°F | 55°F | 0.1" |
| June | 52°F | 64°F | 57°F | 0.0" |
| July | 54°F | 64°F | 58°F | 0.0" |
| August | 54°F | 65°F | 59°F | 0.0" |
| September | 54°F | 68°F | 60°F | 0.0" |
| October | 52°F | 69°F | 59°F | 0.3" |
| November | 48°F | 65°F | 55°F | 0.6" |
| December | 44°F | 60°F | 50°F | 0.1" |
| Index | Castroville | California | National |
| Air quality index | 37 | 55 | 42 |
| Pollution index | 9,602,130 | 10,473,190 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 330 |
| Days with moderate air quality | 34 |
| Days w/ poor A.Q. for sensitive groups | 1 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.070% |
| Benzene | 0.190% |
| Carbon Tetrachloride | 0.000% |
| Lead | 0.080% |
| Mercury | 0.070% |
| City | Population | Air Quality Index | National Avg. |
| Freedom, CA | 3,959 | 35 | 30.0% |
| Rio del Mar, CA | 9,713 | 35 | 30.0% |
| Interlaken, CA | 7,596 | 35 | 30.0% |
| Watsonville, CA | 52,398 | 35 | 30.0% |
| La Selva Beach, CA | 2,544 | 35 | 30.0% |
| Castroville, CA | 6,332 | 37 | 26.0% |
| City | Population | Air Quality Index | National Avg. |
| Forest Hills, PA | 6,333 | 56 | 12.0% |
| Red Lion, PA | 6,334 | 41 | 18.0% |
| Kingston Estates, NJ | 6,335 | 51 | 2.0% |
| West Point, NY | 6,328 | 36 | 28.0% |
| Perth, ON | 6,328 | n/a | |
| Castroville, CA | 6,332 | 37 | 26.0% |
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