Homicides are down dramatically in the District and other cities across America at the same time many parts of the nation are experiencing the coolest summer in decades. That has some experts wondering if the big chill is allowing cooler heads to prevail on city streets.

“The hard science is not conclusive,” said George Washington University criminologist Paul Butler, a former federal prosecutor. But “it’s probably true that the cooler weather is responsible for the drop in violent crime. Any beat cop will tell you that a cooler summer means safer streets.”