Does humid air make cool weather feel cooler?
The amount of humidity in the air by itself doesn’t make any difference in how cold the air “feels.” Sometimes you will hear that the water vapor in the air carries heat away, cooling you faster. At first glance that might seem to make sense because most people have heard of victims of boating accidents dying because they weren’t pulled from chilly water before dying of hypothermia — a cooling of the body’s core temperature. In these cases the water does quickly carry heat away from the body and people with no protection can die quickly in 40-degree water. But, even on the most humid of days, especially when the air is chilly, the percentage of water molecules in the air as water vapor is very small. Even if water molecules did carry heat away from your body, there are too few to noticeably cool you. Also, it turns out that water vapor molecules are no better at conducting heat than the nitrogen and oxygen molecules that make up most of the air.
