| 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 | Mechanicsville | Maryland | National |
| Air quality index | 47 | 43 | 42 |
| Pollution index | 384,133 | 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 | 0.010% |
| Carbon Tetrachloride | 0.001% |
| Lead | 0.003% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| Prince Frederick, MD | 2,709 | 41 | 18.0% |
| St. Leonard, MD | 549 | 41 | 18.0% |
| Leonardtown, MD | 3,795 | 41 | 18.0% |
| Calvert Beach, MD | 860 | 41 | 18.0% |
| Broomes Island, MD | 513 | 41 | 18.0% |
| Mechanicsville, MD | 1,724 | 47 | 6.0% |
| City | Population | Air Quality Index | National Avg. |
| Hazen, AR | 1,724 | 45 | 10.0% |
| De Pue, IL | 1,724 | 0 | 100.0% |
| Heidelberg, TX | 1,724 | 42 | 16.0% |
| Runaway Bay, TX | 1,724 | 33 | 34.0% |
| Duxbury, MA | 1,723 | 43 | 14.0% |
| Mechanicsville, MD | 1,724 | 47 | 6.0% |
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