| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 28°F | 49°F | 38°F | 6.6" |
| February | 29°F | 52°F | 40°F | 4.8" |
| March | 36°F | 61°F | 48°F | 6.3" |
| April | 46°F | 72°F | 59°F | 6.8" |
| May | 55°F | 79°F | 66°F | 7.2" |
| June | 64°F | 87°F | 75°F | 8.1" |
| July | 68°F | 90°F | 78°F | 6.8" |
| August | 66°F | 88°F | 77°F | 7.1" |
| September | 60°F | 82°F | 70°F | 6.7" |
| October | 49°F | 72°F | 59°F | 8.4" |
| November | 38°F | 62°F | 49°F | 8.3" |
| December | 32°F | 53°F | 42°F | 8.0" |
| Index | Dumbarton | Virginia | National |
| Air quality index | 44 | 58 | 42 |
| Pollution index | 5,336,070 | 1,561,881 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 272 |
| Days with moderate air quality | 93 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.200% |
| Benzene | 0.050% |
| Carbon Tetrachloride | 0.010% |
| Lead | 0.050% |
| Mercury | 0.010% |
| City | Population | Air Quality Index | National Avg. |
| Brandermill, VA | 13,887 | 44 | 12.0% |
| Wyndham, VA | 11,656 | 44 | 12.0% |
| Bon Air, VA | 17,599 | 44 | 12.0% |
| Lakeside, VA | 12,749 | 44 | 12.0% |
| Richmond, VA | 229,233 | 44 | 12.0% |
| Dumbarton, VA | 8,411 | 44 | 12.0% |
| City | Population | Air Quality Index | National Avg. |
| Westwego, LA | 8,411 | 45 | 10.0% |
| Heber, CA | 8,413 | 58 | 16.0% |
| Spring Valley Lake, CA | 8,408 | 89 | 78.0% |
| Greenville, MI | 8,407 | 38 | 24.0% |
| Hyrum, UT | 8,415 | 44 | 12.0% |
| Dumbarton, VA | 8,411 | 44 | 12.0% |
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