Seattle residents may have oohed and aahed at a double rainbow that briefly appeared Tuesday evening, but weather experts say the Instagram-worthy sight isn’t that rare.

“Rainbows are not uncommon, especially around here,” National Weather Service meteorologist Courtney Obergsell said Wednesday morning.

Even double rainbows “can happen quite frequently,” Obergsell said.

Rainbows do require certain atmospheric conditions and sunlight for us to see them, according to the weather service. Light entering a water droplet reflects off the inside, separating into colors. The light makes a rainbow as it exits the droplet.

The sun has to be behind you in order for you to see a rainbow, and the clouds have to have cleared.

A double rainbow occurs when the refracted light reflects off the raindrop’s surface a second time, creating a fainter arc with the order of colors reversed.

The Seattle region happens to experience those required conditions a lot, including amid Tuesday’s rain and sun breaks.

Advertising

It also rained more on Tuesday than it did in all of May last year, according to the weather service.

About 0.13 inches of rain fell on Seattle in six hours on Tuesday. Last May saw 0.12 inches, which makes it tied for the driest May on record.