| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 27°F | 41°F | 35°F | 2.2" |
| February | 28°F | 45°F | 37°F | 1.4" |
| March | 36°F | 54°F | 45°F | 4.8" |
| April | 46°F | 65°F | 56°F | 1.6" |
| May | 55°F | 73°F | 65°F | 8.1" |
| June | 64°F | 82°F | 75°F | 3.0" |
| July | 70°F | 87°F | 80°F | 0.5" |
| August | 67°F | 84°F | 76°F | 1.1" |
| September | 61°F | 78°F | 70°F | 1.7" |
| October | 50°F | 68°F | 59°F | 7.1" |
| November | 39°F | 57°F | 48°F | 2.9" |
| December | 33°F | 47°F | 40°F | 4.4" |
| Index | Fallston | Maryland | National |
| Air quality index | 46 | 43 | 42 |
| Pollution index | 9,823,920 | 5,342,367 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 223 |
| Days with moderate air quality | 129 |
| Days w/ poor A.Q. for sensitive groups | 13 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.010% |
| Benzene | 0.070% |
| Carbon Tetrachloride | 0.050% |
| Lead | 0.030% |
| Mercury | 0.140% |
| City | Population | Air Quality Index | National Avg. |
| New Freedom, PA | 4,691 | 41 | 18.0% |
| Fawn Grove, PA | 462 | 41 | 18.0% |
| Pylesville, MD | 1,015 | 45 | 10.0% |
| Darlington, MD | 522 | 45 | 10.0% |
| Delta, PA | 513 | 45 | 10.0% |
| Fallston, MD | 9,118 | 46 | 8.0% |
| City | Population | Air Quality Index | National Avg. |
| Yorkshire, VA | 9,118 | 47 | 6.0% |
| Clinton, OK | 9,117 | 43 | 14.0% |
| Columbia City, IN | 9,115 | 45 | 10.0% |
| Greenville, RI | 9,114 | 44 | 12.0% |
| New Glasgow, NS | 9,114 | n/a | |
| Fallston, MD | 9,118 | 46 | 8.0% |
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