ASK THE METEOROLOGIST
“Can rain evaporate before it hits the ground?”
William, Mr. Ward’ 6th Grade Class
St. Mary’s School
Rain can certainly evaporate before reaching the ground and this is something we see quite often around here! This is very common during the summer months and right now, as we head into fall. Here’s why it happens — summertime here in Southern Oregon is pretty brutal. The very dry heat brings temperatures well into the 90′s for much of the June, July and August. Because the air near the ground is so warm and so dry, any rain that does fall does not have the ability to make it to the ground. It will evaporate before doing so. This is know as virga!
Virga is the reason this area has dry thunderstorms. The rainfall produced from many of our thunderstorms in the summer does not reach the ground. This leads to dry lightning and wildfires like the current ones burning in our region.
Another example of rain evaporating before reaching the ground is the pyrocumulus clouds, a direct result of extensive heat released from wildfires. Pyrocumlus clouds can produce rainfall ..often times the radar will pick up this rainfall or other particulates that fire has suspended well into the atmosphere. If there is enough heat and rising air, pyrocumulus clouds can turn into pyrocumulonimbus clouds (a thunderstorm cloud), producing their own rainfall and lightning. In both cases, the radar will detect precipitation or some type of matter susupended in the air …but the rain does not reach the ground due to the extensive heat near the surface where the flames are!