Ominous clouds gathered over a Michigan city on Monday night, leading residents to question what was causing the bulbous formations and if they were a sign of rough weather ahead.
As the orange-tinged clouds were spotted at about 8.30pm above Iron Mountain, residents posted pictures of them on social media to see if anyone could identify what they were.
Meteorologist Jeff Last was finally able to resolve the mystery through Twitter, when he identified the phenomenon as Mammatus.