| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 45°F | 69°F | 56°F | 3.3" |
| February | 46°F | 70°F | 57°F | 2.5" |
| March | 49°F | 73°F | 60°F | 2.0" |
| April | 52°F | 75°F | 62°F | 0.6" |
| May | 56°F | 78°F | 65°F | 0.2" |
| June | 60°F | 83°F | 70°F | 0.0" |
| July | 65°F | 89°F | 75°F | 0.0" |
| August | 65°F | 90°F | 75°F | 0.0" |
| September | 63°F | 89°F | 74°F | 0.2" |
| October | 57°F | 82°F | 68°F | 0.5" |
| November | 50°F | 76°F | 62°F | 0.6" |
| December | 44°F | 68°F | 55°F | 2.1" |
| Index | Pasadena | 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. |
| Commerce, CA | 12,738 | 72 | 44.0% |
| Pico Rivera, CA | 62,507 | 72 | 44.0% |
| La Cañada Flintridge, CA | 20,078 | 72 | 44.0% |
| Avocado Heights, CA | 13,836 | 72 | 44.0% |
| El Monte, CA | 113,917 | 72 | 44.0% |
| Pasadena, CA | 142,017 | 72 | 44.0% |
| City | Population | Air Quality Index | National Avg. |
| Milton, ON | 142,128 | n/a | |
| Murfreesboro, TN | 141,704 | 45 | 10.0% |
| Mesquite, TX | 142,429 | 51 | 2.0% |
| Syracuse, NY | 142,553 | 37 | 26.0% |
| McAllen, TX | 142,557 | 42 | 16.0% |
| Pasadena, CA | 142,017 | 72 | 44.0% |
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