Freezing temperatures forecast have meteorologists warning Puget Sound residents to cover their sensitive plants overnight, in a frost advisory in effect from 11 p.m. Monday to 10 a.m. Tuesday.
"Outlying areas, mainly away from the water, you can pretty much expect freezing temperatures tonight," National Weather Service meteorologist Art Gaebel said.
It's expected to be as cold as the upper 20s and mid 30s, according to the advisory.
While temperatures should be in the 50s Tuesday, Gaebel said they may drop again that night.
By Wednesday, lows should be in the 40s again, he said: "When the clouds and the rain comes back."
That's because, as the Earth loses heat to outer space at night, clear skies speed up the process.
"It's just radiational cooling," Gaebel said. "Once the sun goes down, the Earth loses all of its heat."
Or as NASA explains it on its Earth Observatory website: Clouds "trap some of the outgoing infrared radiation emitted by the Earth and radiate it back downward," warming the planet's surface.
And until that warms Puget Sound enough to keep the frost away, meteorologists suggest residents protect their plants.