NORFOLK, Va. — The old saying goes “it’s not the heat, it’s the humidity!” And while that may be true, it’s only half of the story. It’s the “dew point” that really matters. But what is the dew point?

Ever stepped outside on a crisp autumn morning, taken a deep breath, and noticed that thin, glassy shimmer covering your car or the grass beneath your feet? That’s morning dew—a quiet, sparkling ...