Weather Why: Mammatus clouds & how they're formed

MISSOULA, Mont. — Mammatus clouds made an appearance over western Montana on Wednesday, and our viewers submitted great photos to us!

The big question now is what are mammatus clouds?

Mammatus are actually the smooth bumps you see protruding from under these clouds. They can be opaque or translucent, which is why you can see so many different colors in our viewers' photos.

Some mammatus clouds look a little scary, but they are actually harmless. They do usually accompany storms, but mammatus themselves don't produce severe weather. Normally, they are in front of or behind storms.

There are a lot of theories as to how they are formed, but the simplest is that moist air essentially sinks into dry air within the cloud. This causes the cloud to destabilize and flip over.

So mammatus are basically upside-down clouds!

Do you have any photos you would like to share? Submit them at nbcmontana.com/chimein.