| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 26°F | 40°F | 32°F | 4.1" |
| February | 19°F | 38°F | 28°F | 2.9" |
| March | 29°F | 49°F | 39°F | 4.6" |
| April | 40°F | 63°F | 51°F | 6.6" |
| May | 47°F | 74°F | 61°F | 2.5" |
| June | 61°F | 84°F | 72°F | 9.0" |
| July | 64°F | 84°F | 74°F | 11.6" |
| August | 65°F | 84°F | 74°F | 4.1" |
| September | 57°F | 81°F | 69°F | 2.3" |
| October | 50°F | 69°F | 58°F | 8.8" |
| November | 34°F | 55°F | 44°F | 3.7" |
| December | 25°F | 40°F | 33°F | 5.2" |
| Index | Atglen | Pennsylvania | National |
| Air quality index | 45 | 45 | 42 |
| Pollution index | 2,654,190 | 4,584,805 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 238 |
| Days with moderate air quality | 117 |
| Days w/ poor A.Q. for sensitive groups | 9 |
| Days with unhealthy air quality | 1 |
| Pollutant | Total |
| Arsenic | 0.002% |
| Benzene | 0.030% |
| Carbon Tetrachloride | 0.004% |
| Lead | 0.000% |
| Mercury | 0.005% |
| City | Population | Air Quality Index | National Avg. |
| Modena, PA | 655 | 42 | 16.0% |
| Elverson, PA | 1,369 | 42 | 16.0% |
| Goodville, PA | 334 | 42 | 16.0% |
| Caln, PA | 1,335 | 42 | 16.0% |
| South Coatesville, PA | 1,559 | 42 | 16.0% |
| Atglen, PA | 1,160 | 45 | 10.0% |
| City | Population | Air Quality Index | National Avg. |
| Mount Ida, AR | 1,160 | 38 | 24.0% |
| Third Lake, IL | 1,160 | 39 | 22.0% |
| Mahnomen, MN | 1,160 | 33 | 34.0% |
| Avonmore, PA | 1,160 | 38 | 24.0% |
| Fairhope, PA | 1,160 | 36 | 28.0% |
| Atglen, PA | 1,160 | 45 | 10.0% |
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