Heavy mammatus – or ‘mammary’ – clouds were seen over Tulsa, Oklahoma, on April 28 after a severe tornado-warned storm swept through the city and surrounding counties.
In this video, the cloud formation – made up of bulges or pouches at the base of other clouds – can be seen covering the sky at sunset. The clouds are said to form as a result of air turbulence within large cumulonimbus structures.
The NWS lifted the tornado warning for Tulsa at 6.45pm. Credit: RJ Goodeyon via Storyful