| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 24°F | 39°F | 31°F | 2.9" |
| February | 26°F | 42°F | 33°F | 2.8" |
| March | 34°F | 53°F | 43°F | 4.1" |
| April | 44°F | 65°F | 54°F | 4.9" |
| May | 53°F | 73°F | 63°F | 4.8" |
| June | 62°F | 82°F | 71°F | 5.4" |
| July | 66°F | 86°F | 76°F | 4.0" |
| August | 64°F | 84°F | 73°F | 4.2" |
| September | 58°F | 77°F | 67°F | 5.2" |
| October | 48°F | 67°F | 57°F | 5.8" |
| November | 38°F | 55°F | 46°F | 3.1" |
| December | 31°F | 45°F | 38°F | 4.6" |
| Index | Gettysburg | Pennsylvania | National |
| Air quality index | 42 | 45 | 42 |
| Pollution index | 5,553,870 | 4,584,805 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 288 |
| Days with moderate air quality | 77 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.004% |
| Benzene | 0.070% |
| Carbon Tetrachloride | 0.010% |
| Lead | 0.410% |
| Mercury | 0.070% |
| City | Population | Air Quality Index | National Avg. |
| Fort Ritchie, MD | 48 | 40 | 20.0% |
| Highfield-Cascade, MD | 912 | 40 | 20.0% |
| Pen Mar, PA | 1,185 | 40 | 20.0% |
| Sabillasville, MD | 390 | 40 | 20.0% |
| Thurmont, MD | 6,783 | 40 | 20.0% |
| Gettysburg, PA | 7,684 | 42 | 16.0% |
| City | Population | Air Quality Index | National Avg. |
| Seminole, TX | 7,683 | 45 | 10.0% |
| Fanwood, NJ | 7,686 | 51 | 2.0% |
| Colonie, NY | 7,686 | 37 | 26.0% |
| Plumas Lake, CA | 7,687 | 44 | 12.0% |
| Village St. George, LA | 7,688 | 45 | 10.0% |
| Gettysburg, PA | 7,684 | 42 | 16.0% |
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