| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 25°F | 44°F | 34°F | 2.9" |
| February | 25°F | 47°F | 35°F | 2.9" |
| March | 34°F | 57°F | 45°F | 5.0" |
| April | 43°F | 70°F | 56°F | 4.1" |
| May | 54°F | 77°F | 65°F | 4.0" |
| June | 62°F | 85°F | 73°F | 5.4" |
| July | 67°F | 89°F | 77°F | 9.1" |
| August | 65°F | 87°F | 75°F | 5.1" |
| September | 58°F | 80°F | 68°F | 11.6" |
| October | 46°F | 70°F | 57°F | 7.0" |
| November | 35°F | 58°F | 45°F | 6.5" |
| December | 30°F | 49°F | 39°F | 2.7" |
| Index | Manassas | Virginia | National |
| Air quality index | 47 | 58 | 42 |
| Pollution index | 520,936 | 1,561,881 | 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 | 0.020% |
| Benzene | 0.010% |
| Carbon Tetrachloride | 0.002% |
| Lead | 0.050% |
| Mercury | 0.001% |
| City | Population | Air Quality Index | National Avg. |
| New Baltimore, VA | 11,017 | 38 | 24.0% |
| Bull Run Mountain Estates, VA | 1,777 | 38 | 24.0% |
| Dulles Town Center, VA | 5,362 | 47 | 6.0% |
| Calverton, VA | 72 | 47 | 6.0% |
| Nokesville, VA | 1,366 | 47 | 6.0% |
| Manassas, VA | 41,038 | 47 | 6.0% |
| City | Population | Air Quality Index | National Avg. |
| Oviedo, FL | 41,062 | 37 | 26.0% |
| Hickory, NC | 41,067 | 43 | 14.0% |
| Findlay, OH | 41,098 | 39 | 22.0% |
| Weslaco, TX | 41,103 | 42 | 16.0% |
| Shelton, CT | 41,162 | 41 | 18.0% |
| Manassas, VA | 41,038 | 47 | 6.0% |
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