What City In the United States Has the Highest Relative Humidity On a Hot July Afternoon?

Los Angeles, California, has the highest relative humidity in the United States, where the average July afternoon humidity reaches 68 percent.

Not much better are runner ups San Juan, Puerto Rico (67 percent); San Diego, California (66 percent); Juneau, Alaska (66 percent); New Orleans, Louisiana (66 percent); Miami, Florida (63 percent); Mobile, Alabama (62 percent); and Sault Ste. Marie, Michigan (62 percent).

The term relative humidity is used to describe the amount of water vapor that exists in a gaseous mixture of air and water vapor.