Hot summer night-after-night: U.S. sees alarming jump in temps

WASHINGTON -- America in recent years has been sweltering throughthree times more than its normal share of extra-hot summer nights,government weather records show. And that is a particularly dangeroustrend.

During heat waves, like the one that now has a grip on much of theEast, one of the major causes of heat deaths is the lack of nightcooling that would normally allow a stressed body to recover.

Some scientists say the trend is a sign of man-made globalwarming.

A top federal research …