With colder nighttime temperatures predicted for Friday and Saturday, could we possibly see our first frost of the season?

According to the latest forecast from the National Weather Service, our area will see temperatures in the mid-30’s for the next couple of nights.  Higher elevations, like Lookout Mountain, could see temperatures just above freezing.

So how cold does it have to be to frost?  Technically, frost cannot form until the temperature reaches freezing, 32 degrees.  But, that is air temperature – usually measured at least 5-10 feet off the ground. During the morning hours, frost can begin to form with temperatures as warm as 37 degrees. It’s always colder the closer to the ground you measure the temperature. That can cause frost to form on car windows, grass, and slightly-elevated surfaces that have dipped to the 32-degree mark.

The National Weather Service typically issues frost advisories in the fall when the minimum temperature is forecast to be between 33-36 degrees.  Freeze warnings are issued in the fall when temperatures are expected to be at or below freezing.