| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 39°F | 69°F | 53°F | 4.6" |
| February | 40°F | 68°F | 54°F | 3.4" |
| March | 44°F | 70°F | 56°F | 1.6" |
| April | 46°F | 72°F | 59°F | 1.3" |
| May | 53°F | 73°F | 62°F | 0.8" |
| June | 57°F | 76°F | 66°F | 0.1" |
| July | 60°F | 80°F | 69°F | 0.2" |
| August | 60°F | 81°F | 69°F | 0.1" |
| September | 57°F | 82°F | 69°F | 0.3" |
| October | 50°F | 79°F | 64°F | 1.2" |
| November | 43°F | 75°F | 57°F | 1.6" |
| December | 38°F | 68°F | 52°F | 3.8" |
| Index | Bonsall | 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% |
| Lake San Marcos, CA | 3,957 | 64 | 28.0% |
| Fallbrook, CA | 32,359 | 64 | 28.0% |
| Valley Center, CA | 11,320 | 64 | 28.0% |
| Oceanside, CA | 175,694 | 64 | 28.0% |
| Bonsall, CA | 4,194 | 64 | 28.0% |
| City | Population | Air Quality Index | National Avg. |
| Tiptonville, TN | 4,194 | 26 | 48.0% |
| Spindale, NC | 4,193 | 36 | 28.0% |
| Alfred, NY | 4,193 | 35 | 30.0% |
| Red Rock, AZ | 4,196 | 47 | 6.0% |
| Sutton, QC | 4,196 | n/a | |
| Bonsall, CA | 4,194 | 64 | 28.0% |
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