| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 25°F | 44°F | 34°F | 5.2" |
| February | 26°F | 47°F | 35°F | 6.2" |
| March | 35°F | 57°F | 45°F | 5.0" |
| April | 44°F | 68°F | 55°F | 6.9" |
| May | 52°F | 74°F | 62°F | 6.4" |
| June | 60°F | 82°F | 71°F | 11.7" |
| July | 64°F | 84°F | 73°F | 7.3" |
| August | 63°F | 83°F | 72°F | 6.6" |
| September | 56°F | 77°F | 65°F | 10.4" |
| October | 45°F | 67°F | 55°F | 12.8" |
| November | 34°F | 57°F | 44°F | 5.4" |
| December | 30°F | 49°F | 38°F | 6.2" |
| Index | Merrimac | Virginia | National |
| Air quality index | 41 | 58 | 42 |
| Pollution index | 243,902 | 1,561,881 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 306 |
| Days with moderate air quality | 55 |
| Days w/ poor A.Q. for sensitive groups | 4 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.020% |
| Benzene | 0.003% |
| Carbon Tetrachloride | 0.001% |
| Lead | 0.020% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| Elliston, VA | 1,040 | 41 | 18.0% |
| Belview, VA | 999 | 41 | 18.0% |
| Parrott, VA | 301 | 41 | 18.0% |
| Radford, VA | 17,833 | 41 | 18.0% |
| Lafayette, VA | 813 | 41 | 18.0% |
| Merrimac, VA | 2,893 | 41 | 18.0% |
| City | Population | Air Quality Index | National Avg. |
| Palo Cedro, CA | 2,893 | 42 | 16.0% |
| Deer Lodge, MT | 2,893 | 20 | 60.0% |
| Saint-Alexis-des-Monts, QC | 2,893 | n/a | |
| Yadkinville, NC | 2,892 | 45 | 10.0% |
| Bedford Hills, NY | 2,892 | 43 | 14.0% |
| Merrimac, VA | 2,893 | 41 | 18.0% |
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