| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 48°F | 69°F | 57°F | 2.3" |
| February | 49°F | 69°F | 58°F | 1.9" |
| March | 52°F | 70°F | 60°F | 0.9" |
| April | 54°F | 72°F | 62°F | 0.6" |
| May | 59°F | 73°F | 65°F | 0.3" |
| June | 62°F | 76°F | 67°F | 0.0" |
| July | 66°F | 80°F | 71°F | 0.1" |
| August | 66°F | 82°F | 72°F | 0.0" |
| September | 65°F | 82°F | 72°F | 0.2" |
| October | 60°F | 79°F | 68°F | 0.5" |
| November | 54°F | 75°F | 63°F | 0.7" |
| December | 48°F | 68°F | 57°F | 2.4" |
| Index | Fountain Valley | California | National |
| Air quality index | 72 | 55 | 42 |
| Pollution index | 858,652 | 10,473,190 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 66 |
| Days with moderate air quality | 208 |
| Days w/ poor A.Q. for sensitive groups | 62 |
| Days with unhealthy air quality | 28 |
| Pollutant | Total |
| Arsenic | 0.002% |
| Benzene | 0.010% |
| Carbon Tetrachloride | 0.000% |
| Lead | 0.020% |
| Mercury | 0.001% |
| City | Population | Air Quality Index | National Avg. |
| Cypress, CA | 49,137 | 72 | 44.0% |
| Lakewood, CA | 79,676 | 72 | 44.0% |
| Norwalk, CA | 104,524 | 72 | 44.0% |
| Westminster, CA | 90,857 | 72 | 44.0% |
| East Whittier, CA | 10,182 | 72 | 44.0% |
| Fountain Valley, CA | 56,118 | 72 | 44.0% |
| City | Population | Air Quality Index | National Avg. |
| Tinley Park, IL | 56,082 | 55 | 10.0% |
| Pocatello, ID | 56,016 | 27 | 46.0% |
| New Brunswick, NJ | 55,992 | 41 | 18.0% |
| Valdosta, GA | 56,320 | 35 | 30.0% |
| Smyrna, GA | 56,333 | 52 | 4.0% |
| Fountain Valley, CA | 56,118 | 72 | 44.0% |
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