TIMONIUM, Md.—Here’s a math problem for you. Each United Parcel Service Inc. UPS 2.36% driver makes an average of 120 stops per day. There are ...

This summer, UPS drivers are posting photos of the 120-degree temperatures in their trucks with no A/C. One told us about getting dizzy from the heat.

UPS drivers shared photos of heat readings from their trucks ranging from 116 to 121 degrees. Last week, workers began rallying outside the UPS headquarters for better working conditions.