| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 21°F | 41°F | 31°F | 2.3" |
| February | 21°F | 42°F | 31°F | 2.6" |
| March | 30°F | 54°F | 41°F | 3.0" |
| April | 40°F | 66°F | 53°F | 3.5" |
| May | 50°F | 75°F | 62°F | 4.2" |
| June | 60°F | 82°F | 71°F | 3.7" |
| July | 63°F | 86°F | 75°F | 4.6" |
| August | 61°F | 84°F | 72°F | 4.7" |
| September | 54°F | 78°F | 65°F | 5.1" |
| October | 44°F | 67°F | 55°F | 4.8" |
| November | 33°F | 56°F | 44°F | 2.7" |
| December | 27°F | 46°F | 36°F | 3.3" |
| Index | Littlestown | Pennsylvania | National |
| Air quality index | 42 | 45 | 42 |
| Pollution index | 12,532,500 | 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 | 0.180% |
| Benzene | 0.090% |
| Carbon Tetrachloride | 0.020% |
| Lead | 0.130% |
| Mercury | 0.270% |
| City | Population | Air Quality Index | National Avg. |
| Jefferson borough (Greene County), PA | 252 | 41 | 18.0% |
| Spring Grove, PA | 2,169 | 41 | 18.0% |
| East Berlin, PA | 1,570 | 41 | 18.0% |
| Jefferson, PA | 606 | 41 | 18.0% |
| Hunterstown, PA | 435 | 42 | 16.0% |
| Littlestown, PA | 4,494 | 42 | 16.0% |
| City | Population | Air Quality Index | National Avg. |
| Newton Falls, OH | 4,494 | 42 | 16.0% |
| Whiteland, IN | 4,495 | 54 | 8.0% |
| Poplar Grove, IL | 4,497 | 42 | 16.0% |
| Mount Vernon, MO | 4,490 | 39 | 22.0% |
| Benton, KY | 4,498 | 44 | 12.0% |
| Littlestown, PA | 4,494 | 42 | 16.0% |
Here are the best places to live in Pennsylvania
See the best places to live in Littlestown
Check out the 10 most dangerous cities in Pennsylvania
These are the 10 cheapest cities in Pennsylvania