| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 25°F | 46°F | 34°F | 3.1" |
| February | 25°F | 47°F | 36°F | 2.7" |
| March | 33°F | 58°F | 45°F | 3.6" |
| April | 43°F | 70°F | 56°F | 3.8" |
| May | 52°F | 77°F | 65°F | 4.1" |
| June | 62°F | 86°F | 74°F | 4.7" |
| July | 67°F | 90°F | 78°F | 4.5" |
| August | 65°F | 88°F | 76°F | 4.7" |
| September | 58°F | 82°F | 70°F | 4.3" |
| October | 47°F | 70°F | 58°F | 5.7" |
| November | 36°F | 59°F | 47°F | 2.8" |
| December | 30°F | 50°F | 39°F | 4.3" |
| Index | Severn | Maryland | National |
| Air quality index | 46 | 43 | 42 |
| Pollution index | 14,735,000 | 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 | 0.220% |
| Benzene | 0.090% |
| Carbon Tetrachloride | 0.030% |
| Lead | 0.110% |
| Mercury | 0.270% |
| City | Population | Air Quality Index | National Avg. |
| Gambrills, MD | 2,929 | 46 | 8.0% |
| Pasadena, MD | 29,432 | 46 | 8.0% |
| Edgewater, MD | 8,850 | 46 | 8.0% |
| Columbia, MD | 105,412 | 46 | 8.0% |
| Lansdowne, MD | 8,635 | 46 | 8.0% |
| Severn, MD | 53,374 | 46 | 8.0% |
| City | Population | Air Quality Index | National Avg. |
| Revere, MA | 53,400 | 43 | 14.0% |
| Brandon, MB | 53,334 | n/a | |
| Hoboken, NJ | 53,283 | 51 | 2.0% |
| Pinellas Park, FL | 53,486 | 43 | 14.0% |
| Harrisonburg, VA | 53,558 | 36 | 28.0% |
| Severn, MD | 53,374 | 46 | 8.0% |
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