| 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 | Norwalk | California | National |
| Air quality index | 72 | 55 | 42 |
| Pollution index | 139,490,000 | 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 | 0.200% |
| Benzene | 0.950% |
| Carbon Tetrachloride | 0.080% |
| Lead | 1.320% |
| Mercury | 0.440% |
| City | Population | Air Quality Index | National Avg. |
| Citrus, CA | 10,105 | 72 | 44.0% |
| Irwindale, CA | 1,365 | 72 | 44.0% |
| Valinda, CA | 22,665 | 72 | 44.0% |
| West Puente Valley, CA | 23,555 | 72 | 44.0% |
| West Athens, CA | 9,554 | 72 | 44.0% |
| Norwalk, CA | 104,524 | 72 | 44.0% |
| City | Population | Air Quality Index | National Avg. |
| Green Bay, WI | 104,508 | 36 | 28.0% |
| Wichita Falls, TX | 104,657 | 26 | 48.0% |
| Clarington, ON | 104,855 | n/a | |
| San Tan Valley, AZ | 104,936 | 74 | 48.0% |
| Allen, TX | 104,040 | 51 | 2.0% |
| Norwalk, CA | 104,524 | 72 | 44.0% |
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