| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 29°F | 46°F | 37°F | 2.8" |
| February | 29°F | 48°F | 38°F | 2.4" |
| March | 38°F | 58°F | 47°F | 3.4" |
| April | 47°F | 69°F | 58°F | 4.2" |
| May | 57°F | 77°F | 67°F | 3.8" |
| June | 66°F | 85°F | 75°F | 4.4" |
| July | 71°F | 88°F | 79°F | 4.6" |
| August | 68°F | 85°F | 76°F | 4.1" |
| September | 62°F | 80°F | 70°F | 4.7" |
| October | 52°F | 71°F | 61°F | 5.8" |
| November | 41°F | 60°F | 50°F | 3.2" |
| December | 34°F | 51°F | 42°F | 3.6" |
| Index | Montross | Virginia | National |
| Air quality index | 41 | 58 | 42 |
| Pollution index | 384,133 | 1,561,881 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 304 |
| Days with moderate air quality | 58 |
| Days w/ poor A.Q. for sensitive groups | 3 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.010% |
| Benzene | 0.010% |
| Carbon Tetrachloride | 0.001% |
| Lead | 0.003% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| Leonardtown, MD | 3,918 | 41 | 18.0% |
| Tappahannock, VA | 1,980 | 44 | 12.0% |
| Warsaw, VA | 2,453 | 44 | 12.0% |
| Rock Point, MD | 64 | 47 | 6.0% |
| Colonial Beach, VA | 3,675 | 47 | 6.0% |
| Montross, VA | 568 | 41 | 18.0% |
| City | Population | Air Quality Index | National Avg. |
| St. Leonard, MD | 568 | 41 | 18.0% |
| Kirkersville, OH | 568 | 46 | 8.0% |
| Noxen, PA | 568 | 38 | 24.0% |
| Portland, PA | 568 | 34 | 32.0% |
| Montrose, SD | 568 | 36 | 28.0% |
| Montross, VA | 568 | 41 | 18.0% |