| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 45°F | 69°F | 56°F | 7.4" |
| February | 47°F | 68°F | 57°F | 5.5" |
| March | 50°F | 71°F | 60°F | 2.6" |
| April | 52°F | 73°F | 62°F | 1.3" |
| May | 57°F | 74°F | 64°F | 2.3" |
| June | 60°F | 77°F | 67°F | 0.1" |
| July | 64°F | 81°F | 71°F | 0.5" |
| August | 64°F | 83°F | 72°F | 0.2" |
| September | 62°F | 84°F | 71°F | 5.2" |
| October | 57°F | 80°F | 67°F | 1.7" |
| November | 50°F | 74°F | 61°F | 2.9" |
| December | 44°F | 67°F | 55°F | 7.6" |
| Index | Westminster | 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. |
| Bell Gardens, CA | 42,827 | 72 | 44.0% |
| Fullerton, CA | 146,103 | 72 | 44.0% |
| Lakewood, CA | 81,936 | 72 | 44.0% |
| Norwalk, CA | 107,725 | 72 | 44.0% |
| South Whittier, CA | 59,924 | 72 | 44.0% |
| Westminster, CA | 93,920 | 72 | 44.0% |
| City | Population | Air Quality Index | National Avg. |
| Deltona, FL | 93,968 | 37 | 26.0% |
| Suffolk, VA | 93,841 | 40 | 20.0% |
| Santa Monica, CA | 93,745 | 72 | 44.0% |
| San Leandro, CA | 93,731 | 40 | 20.0% |
| Santa Barbara, CA | 94,185 | 44 | 12.0% |
| Westminster, CA | 93,920 | 72 | 44.0% |