All of the major U.S. carriers—Verizon, AT&T, T-Mobile and Sprint—are launching 5G signals across the U.S. The Wall Street Journal's Joanna Stern embarked on a summer 5G testing tour only to learn that 5G is blazing fast... if you're outside, near a cell tower, with some way to keep the phone cool.

Photo Illustration: Adele Morgan

#WSJ #5G