TAMPA, Fla. (WFLA) — The humidity is back on the rise in Tampa Bay and that means foggier mornings. You may also notice pesky condensation on your windows when you get in your car that impairs your visibility through your windshield.

What’s happening?

The air temperature is warm and there is plenty of moisture in the air outside the car. In other words, it is humid!

However, the temperature of the glass windshield is actually colder than the air temperature because it has a low specific heat. In other words, it cools down faster than the air since it is a relatively good conductor and poor insulator. That’s why you have double pane windows! Air traps the heat in-between two panes of glass.

When the temperature reaches the dew point temperature, saturation occurs and condensation is possible. The higher the dew point, the more moisture available in the air to condense out.

The temperature of the glass is close to the dew point temperature of the outside air. Water vapor in the air condenses out into liquid droplets on the cooler windshield.

It’s the opposite of evaporation. The water vapor in gas form is cooling down to become liquid form on the windshield. Once the temperature warms up, evaporation will occur because the air is no longer saturated.

How to clear your windows

  1. Start your car five minutes early.
  2. Use windshield wipers to clear away big water droplets.
  3. Turn the defrost ON and set the temperature to be warm, not cold.
  4. Turn OFF the recirculate, so the humidity levels equalize inside and outside the car.
  5. Let it run until the water droplets have evaporated back into gas form into the air and off the windshield!

This doesn’t happen in the afternoons because the air temperatures and windshield temperatures are much warmer than the dew point, so condensation is not going to occur because the air is not fully saturated.