Why is the ground wet every morning, but it didn’t rain?
SEATTLE — The Q13 News digital team has a saying:
“There are no stupid questions… when it comes to weather.”
We’ve asked the weather team some doozies over the years, including our everyday winter ask of “is it going to snow soon?”
So when we wondered allowed “why is the ground wet when it’s sunny out,” we thought we’d get an eye roll.
Yes, the answer is fairly simple. But it’s not without nuances.
A quick Google search of the question brings back a simple word: Dew. Q13 Chief Meterologist Walter Kelley confirms the wettness on the concrete and in the shadows is indeed dew.
“The air cools to the dew point,” Kelley said. “That is the temperature in which air condenses enough to form dew or in this case make the ground wet. If there is enough moisture you get fog. You can visualize ‘morning dew.'”
The pretty morning dew can also turn into something treacherous: black ice. Black ice can form when the temperature drops below the dew point, and then freezes. Though it hasn’t rained, drivers still need to watch out for slick roads on these clear mornings.
We’ve seen a lot of foggy mornings lately. But even when it isn’t foggy, the air is still cool enough to condense the air.
Q13 News Meterologist M.J. McDermott says the longer we stay in a sunny, dry pattern, the less moisture we’ll see on the ground.
“The longer the high pressure, the drier it gets,” McDermott said. “The dewpoint gets really low as the atmosphere dries out. Until there is no fog, no frost, no ice, just bone dry conditions.”
Fog and dew get rarer in drier conditions. With no rain in the forecast for at least the next seven days, we could see less and less wet concrete.