| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 26°F | 45°F | 35°F | 4.6" |
| February | 27°F | 48°F | 37°F | 4.1" |
| March | 36°F | 59°F | 47°F | 5.4" |
| April | 45°F | 70°F | 57°F | 6.6" |
| May | 54°F | 77°F | 66°F | 7.2" |
| June | 63°F | 86°F | 74°F | 10.2" |
| July | 67°F | 89°F | 78°F | 8.7" |
| August | 66°F | 87°F | 76°F | 7.4" |
| September | 59°F | 81°F | 69°F | 11.4" |
| October | 48°F | 70°F | 58°F | 8.8" |
| November | 37°F | 59°F | 47°F | 5.7" |
| December | 31°F | 50°F | 40°F | 5.9" |
| Index | Accokeek | Maryland | National |
| Air quality index | 47 | 43 | 42 |
| Pollution index | 1,217,530 | 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 | 0.001% |
| Benzene | 0.020% |
| Carbon Tetrachloride | 0.001% |
| Lead | 0.000% |
| Mercury | 0.001% |
| City | Population | Air Quality Index | National Avg. |
| Hybla Valley, VA | 18,438 | 47 | 6.0% |
| Lincolnia, VA | 22,579 | 47 | 6.0% |
| Rose Hill, VA | 21,846 | 47 | 6.0% |
| West Falls Church, VA | 31,262 | 47 | 6.0% |
| Arlington, VA | 236,434 | 47 | 6.0% |
| Accokeek, MD | 11,590 | 47 | 6.0% |
| City | Population | Air Quality Index | National Avg. |
| L'Île-Perrot, QC | 11,591 | n/a | |
| Cedarburg, WI | 11,592 | 44 | 12.0% |
| Nelson, BC | 11,592 | n/a | |
| North Saanich, BC | 11,587 | n/a | |
| Clayton, CA | 11,585 | 40 | 20.0% |
| Accokeek, MD | 11,590 | 47 | 6.0% |
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