| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 41°F | 66°F | 53°F | 11.8" |
| February | 46°F | 68°F | 56°F | 7.0" |
| March | 49°F | 69°F | 58°F | 1.6" |
| April | 50°F | 69°F | 59°F | 2.3" |
| May | 56°F | 72°F | 64°F | 0.3" |
| June | 57°F | 72°F | 64°F | 0.2" |
| July | 62°F | 76°F | 68°F | 0.1" |
| August | 63°F | 78°F | 70°F | 7.0" |
| September | 55°F | 76°F | 65°F | 0.5" |
| October | 51°F | 75°F | 62°F | 1.3" |
| November | 47°F | 72°F | 58°F | 3.1" |
| December | 40°F | 65°F | 52°F | 3.3" |
| Index | Oceanside | California | National |
| Air quality index | 64 | 55 | 42 |
| Pollution index | 45,820,500 | 10,473,190 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 87 |
| Days with moderate air quality | 253 |
| Days w/ poor A.Q. for sensitive groups | 23 |
| Days with unhealthy air quality | 2 |
| Pollutant | Total |
| Arsenic | 1.130% |
| Benzene | 0.410% |
| Carbon Tetrachloride | 0.030% |
| Lead | 0.600% |
| Mercury | 0.080% |
| City | Population | Air Quality Index | National Avg. |
| Camp Pendleton South, CA | 16,618 | 64 | 28.0% |
| Encinitas, CA | 62,967 | 64 | 28.0% |
| San Marcos, CA | 96,219 | 64 | 28.0% |
| Fallbrook, CA | 32,359 | 64 | 28.0% |
| Fairbanks Ranch, CA | 2,929 | 64 | 28.0% |
| Oceanside, CA | 175,694 | 64 | 28.0% |
| City | Population | Air Quality Index | National Avg. |
| Oshawa, ON | 176,009 | n/a | |
| Elk Grove, CA | 173,370 | 52 | 4.0% |
| Rancho Cucamonga, CA | 178,060 | 89 | 78.0% |
| Ontario, CA | 178,194 | 89 | 78.0% |
| Santa Rosa, CA | 178,391 | 34 | 32.0% |
| Oceanside, CA | 175,694 | 64 | 28.0% |
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