A highstorm is a fierce weather system on the planet of Roshar. They occur once every few days, or at command of the Stormfather, and move from stormward to leeward from the Origin. East of Roshar, the highstorms are incredibly destructive. They progress across the continent, though they weaken gradually as they cross, and are mostly broken by the mountains east of Shinovar. On the Shattered Plains refuse and litter is piled high to be carried away by the highstorm when it arrives, a practice usually frowned upon as the trash may wind up hitting another city, but found acceptable on the Shattered Plains only because there is literally no other semblance of civilisation nearby for the trash to hit.
A highstorm has three general stages. The leading edge, or stormwall, is the most dangerous part of the storm. Immensely powerful winds generate a wall of dust, water, and larger debris. It is shown that it is powerful enough to carry large trees at least 640 kilometres, into the Shattered Plains. It was also powerful enough to hurl boulders hundreds of metres vertically into the air during Kaladin and Szeths second battle. The main body of the highstorm carries less debris, although the winds are still strong enough to hurl boulders. The trailing edge of the storm, known as the riddens, consists of light rains mixed with relatively mild gusts of wind.  The Purelake experiences less intense highstorms.
Highstorms are the single most important force in Roshar's ecology. Some plants, like lavis polyps, enclose themselves against the highstorm's fury; others retract or fold their relatively fragile leaves, vines, or roots away. Stormwater is better for plants than regular water,, providing nutrients that would otherwise be provided by soil swept away by the highstorms. Rosharan fauna has adapted as well; species like axehounds and whitespines are covered in carapaces, and chasmfiend gemhearts glow when extracted, hinting at a symbiotic relationship with spren that requires Stormlight, and, thus, highstorms, to function.
Many cities have protection against the storms. Kholinar has its windblades—large stone formations that divert the highstorm's force— and Sesemalex Dar has troughs that prevent the city from flooding. Many curses are related to the highstorms, and the Shin reverence for stone may be at least partly due to the mountain range that protects Shinovar from the brunt of the highstorm's power.
Stormwardens try to predict when highstorms occur, and have become somewhat accurate, though not always. The Stormwardens have negative connotations since predicting the future is forbidden under Vorin doctrine.
Vorin mythology claims that each storm is born in the east at the Origin before traveling west across Roshar, but modern Stormwardens believe there exists a single highstorm that travels around the planet, with the length between storms decided by the speed it travels during that time of year.
It has been stated by Zahel that the highstorms are Invested. As mentioned above, during a highstorm Parshendi become able to bond with spren. This is done through a ritual that involves the Rider of Storms, who appears at a certain point during the storm.
- The Way of Kings chapter 12
- The Way of Kings interlude I-4
- Words of Radiance chapter 49
- The Way of Kings chapter 34
- Words of Radiance chapter 69
- Words of Radiance chapter 86
- The Way of Kings chapter 35
- The Way of Kings interlude I-1
- The Way of Kings chapter 11
- The Way of Kings chapter 60
- The Way of Kings chapter 55
- The Way of Kings chapter 44
- The Way of Kings chapter 18
- Words of Radiance chapter 87
- Words of Radiance interlude I-6