| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 29°F | 46°F | 37°F | 2.6" |
| February | 29°F | 48°F | 38°F | 2.4" |
| March | 37°F | 56°F | 46°F | 3.4" |
| April | 47°F | 68°F | 57°F | 4.0" |
| May | 57°F | 75°F | 66°F | 4.0" |
| June | 66°F | 84°F | 75°F | 4.9" |
| July | 71°F | 88°F | 79°F | 3.9" |
| August | 69°F | 86°F | 77°F | 5.1" |
| September | 63°F | 80°F | 71°F | 4.1" |
| October | 52°F | 70°F | 61°F | 6.2" |
| November | 41°F | 59°F | 50°F | 3.2" |
| December | 33°F | 51°F | 42°F | 3.7" |
| Index | Leonardtown | Maryland | National |
| Air quality index | 41 | 43 | 42 |
| Pollution index | 384,133 | 5,342,367 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 304 |
| Days with moderate air quality | 58 |
| Days w/ poor A.Q. for sensitive groups | 3 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.010% |
| Benzene | 0.010% |
| Carbon Tetrachloride | 0.001% |
| Lead | 0.003% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| Lusby, MD | 2,180 | 41 | 18.0% |
| St. George Island, MD | 426 | 41 | 18.0% |
| Montross, VA | 553 | 41 | 18.0% |
| Calvert Beach, MD | 860 | 41 | 18.0% |
| Broomes Island, MD | 513 | 41 | 18.0% |
| Leonardtown, MD | 3,795 | 41 | 18.0% |
| City | Population | Air Quality Index | National Avg. |
| North Muskegon, MI | 3,795 | 38 | 24.0% |
| North Wildwood, NJ | 3,794 | 37 | 26.0% |
| Sagamore, MA | 3,792 | 36 | 28.0% |
| Roosevelt Park, MI | 3,792 | 38 | 24.0% |
| Val Verde Park, TX | 3,792 | 25 | 50.0% |
| Leonardtown, MD | 3,795 | 41 | 18.0% |
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