Felicity Lanchester,Felicity Lanchester / Cloud iridescence forming above a cumulonimbus cloud, caused by light refraction through individual water droplets and ice crystals at high altitude, Sierra Leone.

Juan Carlos Munoz / Rain falling from cumulonimbus clouds over the sea, Bahamas, Caribbean

Jim Brandenburg / Prairie under threatening thunder clouds, South Dakota

Jim Brandenburg / Cloudy sky over tallgrass prairie, Wind Cave National Park, South Dakota

Juan Carlos Munoz / Coastal village under cloudy sky. Inisheer, Aran Islands, County Galway, Republic of Ireland. May 2011.

Graham Eaton / Storm clouds (cumulonimbus) building over Minera Moors, with Heather (Calluna vulgaris) in bloom, near Wrexham, Wales, UK, August, August.

Pascal Tordeux / Cumulonimbus clouds above Oilseed rape (Brassica napus) field, Picardy, France, April 2016.

Pascal Tordeux / Baie de Somme / Bay of the Somme with Cumulonimbus clouds, France, April 2016.

Pascal Tordeux / Country track with dark cumulonimbus clouds above, Surfontaine, Picardy, France, March 2016.

Alex Hyde / Detail of Cumulonimbus cloud at sunset. Nordtirol, Austrian Alps. July.

Alex Hyde / Detail of Cumulonimbus cloud at sunset. Nordtirol, Austrian Alps. July.

Tim Fitzharris / Giant cumulonimbus clouds, near Des Moines, New Mexico