| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 26°F | 44°F | 34°F | 3.3" |
| February | 26°F | 46°F | 35°F | 2.6" |
| March | 33°F | 56°F | 44°F | 3.6" |
| April | 44°F | 68°F | 56°F | 4.0" |
| May | 54°F | 77°F | 65°F | 3.9" |
| June | 64°F | 86°F | 74°F | 4.8" |
| July | 70°F | 90°F | 79°F | 5.0" |
| August | 68°F | 87°F | 77°F | 5.8" |
| September | 61°F | 82°F | 71°F | 4.3" |
| October | 50°F | 70°F | 59°F | 4.7" |
| November | 39°F | 59°F | 48°F | 2.8" |
| December | 31°F | 49°F | 40°F | 4.7" |
| Index | Darby | Pennsylvania | National |
| Air quality index | 51 | 45 | 42 |
| Pollution index | 12,485,100 | 4,584,805 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 180 |
| Days with moderate air quality | 169 |
| Days w/ poor A.Q. for sensitive groups | 16 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.020% |
| Benzene | 0.100% |
| Carbon Tetrachloride | 0.100% |
| Lead | 0.120% |
| Mercury | 0.010% |
| City | Population | Air Quality Index | National Avg. |
| Richwood, NJ | 3,967 | 40 | 20.0% |
| Ardentown, DE | 240 | 51 | 2.0% |
| Greenwich, NJ | 2,747 | 51 | 2.0% |
| Brookhaven, PA | 8,045 | 51 | 2.0% |
| Trainer, PA | 1,896 | 51 | 2.0% |
| Darby, PA | 10,711 | 51 | 2.0% |
| City | Population | Air Quality Index | National Avg. |
| Cold Springs, NV | 10,704 | 46 | 8.0% |
| Pleasanton, TX | 10,703 | 49 | 2.0% |
| Memphis, FL | 10,702 | 38 | 24.0% |
| Soquel, CA | 10,721 | 35 | 30.0% |
| Woodbury, NY | 10,700 | 36 | 28.0% |
| Darby, PA | 10,711 | 51 | 2.0% |
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