A heat wave scorched much of the eastern United States over the Fourth of July weekend, bringing extreme temperatures that caused roads to buckle, snarling holiday traffic.

Nowhere was this more dramatic than on a stretch of concrete-paved Interstate 97 south of Baltimore, where one lane of traffic suddenly warped, forcing its closure. A city street in Chicago experienced a similar, though less dramatic, pavement failure, and several state departments of transportation warned motorists to watch for additional heat-related road damage.

Scientists say such heat waves are becoming more common and more intense. Climate change is driving more extreme temperatures, along with heavier rainfall. Both can contribute to pavements expanding and cracking, making roads temporarily impassable as they await expensive repairs. It raises the question: Are the nation's roads ready to meet the challenge of a warmer, wetter future?

Civil engineers say the answers aren't entirely straightforward.