| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 26°F | 41°F | 33°F | 3.2" |
| February | 26°F | 42°F | 33°F | 2.5" |
| March | 34°F | 53°F | 42°F | 6.9" |
| April | 43°F | 65°F | 53°F | 3.6" |
| May | 52°F | 74°F | 63°F | 6.0" |
| June | 61°F | 81°F | 71°F | 6.5" |
| July | 66°F | 86°F | 76°F | 7.9" |
| August | 63°F | 83°F | 73°F | 11.0" |
| September | 56°F | 77°F | 66°F | 6.8" |
| October | 46°F | 66°F | 55°F | 9.4" |
| November | 37°F | 55°F | 45°F | 2.9" |
| December | 31°F | 46°F | 38°F | 7.7" |
| Index | Berwyn | Pennsylvania | National |
| Air quality index | 51 | 45 | 42 |
| Pollution index | 2,169,600 | 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 | 0.010% |
| Benzene | 0.030% |
| Carbon Tetrachloride | 0.002% |
| Lead | 0.010% |
| Mercury | 0.004% |
| City | Population | Air Quality Index | National Avg. |
| Exton, PA | 6,079 | 42 | 16.0% |
| Sanatoga, PA | 8,710 | 42 | 16.0% |
| Eagleview, PA | 1,880 | 42 | 16.0% |
| Lionville, PA | 6,707 | 42 | 16.0% |
| Downingtown, PA | 8,012 | 42 | 16.0% |
| Berwyn, PA | 3,621 | 51 | 2.0% |
| City | Population | Air Quality Index | National Avg. |
| Pine Level, AL | 3,621 | 52 | 4.0% |
| Lake Isabella, CA | 3,621 | 67 | 34.0% |
| Central Gardens, TX | 3,621 | 45 | 10.0% |
| Watertown, CT | 3,620 | 37 | 26.0% |
| Dover Base Housing, DE | 3,620 | 42 | 16.0% |
| Berwyn, PA | 3,621 | 51 | 2.0% |
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