| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 43°F | 63°F | 51°F | 3.0" |
| February | 45°F | 63°F | 53°F | 2.6" |
| March | 46°F | 63°F | 54°F | 2.7" |
| April | 47°F | 64°F | 55°F | 1.2" |
| May | 50°F | 65°F | 56°F | 0.3" |
| June | 52°F | 68°F | 59°F | 0.1" |
| July | 54°F | 69°F | 60°F | 0.0" |
| August | 55°F | 69°F | 60°F | 0.1" |
| September | 54°F | 71°F | 61°F | 0.1" |
| October | 51°F | 70°F | 60°F | 1.0" |
| November | 47°F | 66°F | 55°F | 1.6" |
| December | 42°F | 61°F | 51°F | 2.8" |
| Index | Seaside | 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. |
| Castroville, CA | 6,332 | 37 | 26.0% |
| Marina, CA | 21,966 | 37 | 26.0% |
| Prunedale, CA | 20,560 | 37 | 26.0% |
| Boronda, CA | 1,740 | 37 | 26.0% |
| Del Monte Forest, CA | 3,783 | 37 | 26.0% |
| Seaside, CA | 34,063 | 37 | 26.0% |
| City | Population | Air Quality Index | National Avg. |
| New City, NY | 34,060 | 51 | 2.0% |
| Merritt Island, FL | 33,975 | 36 | 28.0% |
| Pullman, WA | 33,974 | 18 | 64.0% |
| Salisbury, NC | 33,961 | 40 | 20.0% |
| North Ridgeville, OH | 33,961 | 50 | = 100 |
| Seaside, CA | 34,063 | 37 | 26.0% |
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