BLOG: Low near 40 with frost? How can that be?

BLOG: Low near 40 with frost? How can that be?

Tonight's forecast low temperature in Charlotte is 40°. Most areas should reach the mid 30s to low 40s by morning.

There's also a Frost Advisory in effect for all the counties you see shaded in blue.

It seems like that doesn't really add up, does it?

Here's how it works. It's the difference between the temperature (what you see on our current conditions) and the "skin temperature."

The temperature we're all familiar with is measured by an air thermometer. The reading is taken about 1 meter above ground level. Skin temperature is the temperature of the surface layer of the earth. That can vary drastically between day and night and between types of ground cover.

Think about how much different a parking lot feels on a hot summer afternoon compared to how it feels on a summer night. The temperature of the parking lot varies much more than the air a meter above it.

The same principle will be in play Saturday night. Our low temperature will likely remain above freezing. However, the skin temperature may get several degrees cooler as it loses heat due to calm winds and a low dew point (a measure of humidity). The ground surface may get to the freezing mark so frost is possible in some spots.

Bottom line: protect those plants tonight if you're worried about frost. The good news is that after tonight, we look much milder - day and night for the whole extended forecast.

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