It’s warm, moist air from their lungs, droplets of water from around the blowhole, and a certain amount of whale snot.

It follows heavy rainfalls after big plumes of warm, moist air rise up and strong updraughts in the storm clouds sweep water to great heights.

When warm, moist air comes into contact with a cold window or wall, it cools, and the water vapour condenses into drops on the surface.

As that hot, moist air soars upwards it creates lightning that flashes in the thick, smoky gloom.

But even when these storms move across cooler waters, they may still retain extensive remnants of warm and moist air in the upper atmosphere.