July 31, 2015; 4:32 AM ET
Following the steambath of this week, Philadelphia will catch a break from high humidity Friday and this weekend but not sizzling temperatures. more >
Public health officials say the United States is experiencing a resurgence of measles because some parents are opting out of the recommended vaccines for their kids.
This year's flu season is severe. So far, at least 26 children in the United States have died of influenza, and thousands of elderly people have been hospitalized, according to the Centers for Disease Control and Prevention (CDC).
The long, harsh winter at the start of 2014 led some experts to predict that the cold season's "polar vortex" would turn into a "pollen vortex" during the warmer parts of the year, with a massive pollen eruption and a brutal allergy season.