Meaning that even when the Sun is no longer shining, the dewpoint is so high that what might have been a comfortable temperature with a breeze is actually felt

Meaning that even when the Sun is no longer shining, the dewpoint is so high that what might have been a comfortable temperature with a breeze is actually felt as oppressively hot and will cause all sorts of fun mold growing in the home. In the Southeast, AC is also about dehumidifying the air.