| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 30°F | 46°F | 37°F | 5.0" |
| February | 26°F | 43°F | 33°F | 2.2" |
| March | 35°F | 55°F | 44°F | 8.6" |
| April | 44°F | 65°F | 54°F | 8.0" |
| May | 53°F | 74°F | 63°F | 10.0" |
| June | 64°F | 84°F | 73°F | 5.0" |
| July | 68°F | 88°F | 78°F | 5.4" |
| August | 70°F | 88°F | 78°F | 7.3" |
| September | 61°F | 82°F | 71°F | 2.3" |
| October | 53°F | 71°F | 61°F | 14.5" |
| November | 40°F | 59°F | 48°F | 3.8" |
| December | 30°F | 45°F | 37°F | 4.8" |
| Index | Rosaryville | Maryland | National |
| Air quality index | 47 | 43 | 42 |
| Pollution index | 849,185 | 5,342,367 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 209 |
| Days with moderate air quality | 145 |
| Days w/ poor A.Q. for sensitive groups | 10 |
| Days with unhealthy air quality | 1 |
| Pollutant | Total |
| Arsenic | 0.010% |
| Benzene | 0.020% |
| Carbon Tetrachloride | 0.002% |
| Lead | 0.003% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| Chesapeake Beach, MD | 5,996 | 41 | 18.0% |
| Edgewater, MD | 8,850 | 46 | 8.0% |
| Cedarville, MD | 577 | 47 | 6.0% |
| Waldorf, MD | 77,711 | 47 | 6.0% |
| Dunkirk, MD | 2,175 | 47 | 6.0% |
| Rosaryville, MD | 11,344 | 47 | 6.0% |
| City | Population | Air Quality Index | National Avg. |
| Haddonfield, NJ | 11,342 | 51 | 2.0% |
| Pike Creek Valley, DE | 11,346 | 51 | 2.0% |
| Fredericksburg, TX | 11,341 | 49 | 2.0% |
| Fort Meade, MD | 11,340 | 46 | 8.0% |
| Mendota Heights, MN | 11,339 | 46 | 8.0% |
| Rosaryville, MD | 11,344 | 47 | 6.0% |
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