| 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 | Swarthmore | 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. |
| Glassboro, NJ | 20,069 | 40 | 20.0% |
| Richwood, NJ | 3,967 | 40 | 20.0% |
| Exton, PA | 6,079 | 42 | 16.0% |
| Wilmington Manor, DE | 8,335 | 51 | 2.0% |
| Claymont, DE | 9,343 | 51 | 2.0% |
| Swarthmore, PA | 6,339 | 51 | 2.0% |
| City | Population | Air Quality Index | National Avg. |
| Wilmore, KY | 6,339 | 42 | 16.0% |
| Braidwood, IL | 6,338 | 0 | 100.0% |
| Carrollton, VA | 6,340 | 40 | 20.0% |
| Skowhegan, ME | 6,341 | 28 | 44.0% |
| Peachland, BC | 6,336 | n/a | |
| Swarthmore, PA | 6,339 | 51 | 2.0% |
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