I experienced a "cold spot" once, while out walking late on a hot, humid summer night. It was in the center of a crossroad in a dark suburban neighborhood. I was about 20 years old.
It was really cold, in an area about 15 feet across. I lingered there for a few minutes, criss-crossing the area to convince myself it was real. It was too dark to see if my breath was condensing.
(steely)
Cool air can be noticed all the time in the summer. Especially, in low lying areas.
My guess, is Heat Rises.