Heat Island Effect

In the middle of summer here in South Florida, the high temperatures can consistently be in the nineties. Add the 100% humidity and it would feel even warmer, lest the term "feel-like" temperature. It's not just the humidity that makes the temperature "feel-like" it's hotter, but the buildings and constructed surfaces (i.e. sidewalks, streets, and parking lots) are also contributing factors.

USGBC defines heat island effect as:

Warmer temperatures are experienced in urban landscapes compared to adjacent rural areas as a result of solar energy retention.

In other words, you would feel hotter if you were standing in downtown Ft. Lauderdale in the middle of a summer's day - with time and temperature being equal - than if you were standing at Arthur R. Marshall Loxahatchee National Wildlife Refuge.

In addition, the buildings and constructed surfaces retain the heat generated during the day making it seem like the temperature has not let up in the evening. What's happening is the heat is radiating back into the atmosphere off of the buildings and constructed surfaces through convection and conduction as the air temperature becomes cooler at night.