Summer will make a dramatic entrance in the U.S. this week with a heat dome that will bring stifling heat and uncomfortable humidity to millions.

Here are some of the key warning signs to watch for when temperatures rise – and ways to keep cool when the heat and humidity get too high.

Summer will make a dramatic entrance in the U.S. this week with a heat dome that will bring stifling heat and uncomfortable humidity to millions. The heat will be particularly worrisome this ...

Summer will make a dramatic entrance in the U.S. this week with a heat dome that will bring stifling heat and uncomfortable humidity to millions. The heat will be particularly worrisome this ...

Summer will make a dramatic entrance in the U.S. this week with a heat dome that will bring stifling temperatures and uncomfortable humidity to millions. The heat will be particularly worrisome ...

Summer will make a dramatic entrance in the U.S. this week with a heat dome that will bring stifling heat and uncomfortable humidity to millions ...

A heat dome occurs when a large area of high pressure in the upper atmosphere acts as a reservoir that traps heat and humidity, said Ricky Castro, a National Weather Service meteorologist in Illinois.

Summer will make a dramatic entrance in the U.S. this week with a heat dome that will bring stifling heat and uncomfortable humidity to millions. The heat will be particularly worrisome this ...

Summer will make a dramatic entrance in the U.S. this week with a heat dome that will bring stifling temperatures and uncomfortable humidity to millions. The heat will be particularly worrisome thi… ...