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A cloud inversion like this one Rachel Sansom (Cloud Appreciation Society Member 61,044) spotted over the Scottish island of Arran can make it feel as if the sky has been turned upside down. When viewed from clearer air, the cloudscapes spread out below rather than above you. The ‘inversion’ part, however, relates to the profile of air temperatures that lead to these upside-down clouds. In the lower part of our atmosphere, the air at ground level is typically warmer than it is above, with average temperatures steadily decreasing as you go up. But sometimes this pattern is inverted. A layer of warmer air might drift over cooler air in a particular area, whether near the ground or higher up, or perhaps the air at the surface might just be cooled in contact with cold ground or water. Such a temperature inversion can cause inverted clouds.Rachel experienced a cloud inversion at close range when she took part in a guided walk during the Arran Mountain Festival. Her group hiked up through the cloud to emerge into bright sunshine above. This inversion had likely been caused by warm air moving over the cold sea surface around the island. The warmer air above acted as a lid, keeping in place the moist, cloudy air below. Around the time of the hike, Rachel was reaching the conclusion of her PhD research into cloud formation. ‘I’d spent nearly five years thinking about and studying temperature inversions,’ she realised, ‘but never before had I walked through one. It was a very special moment as this project came to a close.’