| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 46°F | 72°F | 57°F | 2.3" |
| February | 48°F | 72°F | 58°F | 1.7" |
| March | 51°F | 75°F | 61°F | 1.0" |
| April | 54°F | 76°F | 64°F | 0.5" |
| May | 58°F | 78°F | 66°F | 0.3" |
| June | 62°F | 81°F | 70°F | 0.0" |
| July | 66°F | 86°F | 74°F | 0.1" |
| August | 66°F | 88°F | 75°F | 0.0" |
| September | 65°F | 88°F | 74°F | 0.2" |
| October | 59°F | 83°F | 69°F | 0.4" |
| November | 52°F | 77°F | 63°F | 0.6" |
| December | 45°F | 70°F | 56°F | 2.5" |
| Index | Placentia | California | National |
| Air quality index | 89 | 55 | 42 |
| Pollution index | 858,652 | 10,473,190 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 42 |
| Days with moderate air quality | 178 |
| Days w/ poor A.Q. for sensitive groups | 79 |
| Days with unhealthy air quality | 58 |
| 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. |
| Baldwin Park, CA | 75,659 | 72 | 44.0% |
| La Puente, CA | 39,780 | 72 | 44.0% |
| Vincent, CA | 16,405 | 72 | 44.0% |
| Fullerton, CA | 141,061 | 72 | 44.0% |
| La Mirada, CA | 48,260 | 72 | 44.0% |
| Placentia, CA | 52,049 | 89 | 78.0% |
| City | Population | Air Quality Index | National Avg. |
| Bentonville, AR | 52,070 | 44 | 12.0% |
| Whitchurch-Stouffville, ON | 52,025 | n/a | |
| Oak Park, IL | 52,102 | 55 | 10.0% |
| Queen Creek, AZ | 52,162 | 74 | 48.0% |
| Mascouche, QC | 52,212 | n/a | |
| Placentia, CA | 52,049 | 89 | 78.0% |
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