Green flash: Conditions right for optical illusion at sunset

CLEVELAND - Want to see the sun turn green? It's an optical illusion that occurs in a flash, maybe a second or two, just as the top of the sun is disappearing over the horizon. And Monday night is a great night to look for it.

The "Green Flash," also known as the "Green Ray," is a visual phenomenon that occurs at sunset. It arises as a by-product of refracted light near the horizon. It's a rare sight because the atmospheric conditions required to produce the green flash aren't common. 

"Conditions have to be just right to see it," said Jay Reynolds from Cleveland State University. "You have to have the right humidity, plus crystal clear skies to see it."

It's only visible in a well-layered atmosphere with little or no turbulence. That doesn't happen very often. But Monday, we will be close to having a very quiet atmosphere.

Reynolds recommends you head to the beach or somewhere near Lake Erie where your view of the horizon will not be blocked. Higher floors of tall buildings will also work.

"Then just watch and wait," he says, "until just a sliver of the sun is left."

Hopefully, you'll see that last sliver of sun turn green for a brief moment.

"It will last for anywhere from one to, perhaps, five seconds," Reynolds said.

One important safety tip: DO NOT look directly at the sun until it is almost set.