Add Yahoo as a preferred source to see more of our stories on Google. Scientists and other observers have become alarmed about the increasing frequency of extreme heat paired with high humidity.

This is an archived article and the information in the article may be outdated. Please look at the time stamp on the story to see when it was last updated. Heat waves are becoming supercharged as the ...

This is an archived article and the information in the article may be outdated. Please look at the time stamp on the story to see when it was last updated. Scientists and other observers have become ...