| 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 | 61 | 55 | 50 |
| Pollution index | 45,820,500 | 18,106,726 | 5,066,862 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 69 |
| Days with moderate air quality | 277 |
| Days w/ poor A.Q. for sensitive groups | 17 |
| Days with unhealthy air quality | 1 |
| Pollutant | Total |
| Arsenic | 1.130% |
| Benzene | 0.410% |
| Carbon Tetrachloride | 0.030% |
| Lead | 0.600% |
| Mercury | 0.080% |
| City, State | Population | Air Quality Index | National Avg. |
| Camp Pendleton South, CA | 12,491 | 61 | 22% |
| Fallbrook, CA | 31,771 | 61 | 22% |
| San Marcos, CA | 91,479 | 61 | 22% |
| Carlsbad, CA | 112,008 | 61 | 22% |
| Lake San Marcos, CA | 4,529 | 61 | 22% |
| Oceanside, CA | 173,829 | 61 | 22% |
| City, State | Population | Air Quality Index | National Avg. |
| Rancho Cucamonga, CA | 173,309 | 85 | 70% |
| Santa Rosa, CA | 173,165 | 35 | 30% |
| Garden Grove, CA | 174,676 | 74 | 48% |
| Tempe, AZ | 174,708 | 74 | 48% |
| Fort Lauderdale, FL | 175,153 | 41 | 18% |
| Oceanside, CA | 173,829 | 61 | 22% |