| 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 | Franconia | Virginia | National |
| Air quality index | 47 | 58 | 42 |
| Pollution index | 2,776,590 | 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 | 0.070% |
| Benzene | 0.020% |
| Carbon Tetrachloride | 0.010% |
| Lead | 0.020% |
| Mercury | 0.030% |
| City | Population | Air Quality Index | National Avg. |
| Lorton, VA | 20,924 | 47 | 6.0% |
| Neabsco, VA | 17,038 | 47 | 6.0% |
| Crosspointe, VA | 5,068 | 47 | 6.0% |
| Floris, VA | 7,752 | 47 | 6.0% |
| Herndon, VA | 24,577 | 47 | 6.0% |
| Franconia, VA | 19,478 | 47 | 6.0% |
| City | Population | Air Quality Index | National Avg. |
| Stillwater, MN | 19,471 | 46 | 8.0% |
| Boone, NC | 19,466 | 26 | 48.0% |
| Salmon Arm, BC | 19,494 | n/a | |
| Orinda, CA | 19,461 | 40 | 20.0% |
| Cumberland, MD | 19,495 | 36 | 28.0% |
| Franconia, VA | 19,478 | 47 | 6.0% |
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