John Polyniak writes from Lake Shore each fall to remind us to swap the heat index for the wind chill. Thanks, John! He asks, "Does humidity, or lack thereof, affect how cold it feels? If so, there should be a 'cold index.'"

It does. And there is.

Damp air feels colder because water conducts heat better than air, so we lose more body heat. AccuWeather adds humidity (plus sunshine, precipitation and altitude) to wind and temperature data to produce its patented "Real Feel" index.