A heat storm as seen in 4 ABY
A heat storm was a common atmospheric phenomenon that frequently swept across the sun-drenched day side of Ryloth. These events occurred due to Ryloth's axis of rotation being nearly parallel with its orbital plane. Heat storms involved intense, swirling winds that could reach speeds of up to 500 kilometers per hour, combined with temperatures exceeding 300 degrees Celsius. They ravaged Ryloth's Bright Lands, incinerating anything in their wake before eventually dissipating on the planet's night side. Being caught in one of these storms almost certainly meant death by incineration.
Clone troopers confront a heat storm on Ryloth during the Clone Wars
To protect themselves from these storms, many cities on Ryloth were built underground. However, the most severe heat storms could even render caves near the surface temporarily uninhabitable. Twi'lek siren whistles were used as warning devices to alert people of the impending arrival of these storms.
In the city of Kala'uun, Twi'lek mothers would tell their children a story about two young lovers named Ko'lek and Oo'rha. Lost in their infatuation, they wandered directly into the path of a heat storm, which resulted in their deaths as they embraced. This tale served as a cautionary measure, intended to discourage children from exploring the dangerous, uncharted tunnels beneath Ryloth's surface.
During 3986 BBY, the Twi'lek Jedi Tott Doneeta attempted to use the Force to control a heat storm that threatened an exiled clan under his protection. This clan was moving through the mountains in search of a new place to call home. As a consequence of his efforts, he suffered severe burns on the left side of his face.