A highstorm is a fierce weather system that traverses the entire continent of Roshar from east to west, starting at the Origin. While highstorms have meteorological significance, they also provide Stormlight, an energy which can be stored within gemstones and power a range of devices and magical abilities.
Highstorms are the fiercest in the stormlands of the east, but gradually subside as they progress westward toward more timid lands. Purelakers, located in the center of the continent, experience weakened storms; Shinovar in the west is spared completely due to the added protection of the Misted Mountains.
The life of a highstorm can be broken down into two stages. The first stage is the most dangerous part of a highstorm: the stormwall. A massive wave of water, reaching several hundred feet in height, casts dirt and debris high into the air; occasional gusts can pick up and toss large objects (such as boulders), hurling them hundreds of feet. As the storm passes by, it gradually grows weaker. The trailing end, or second stage, called the riddens, is simply a light, quiet rainfall. The hour before the riddens is as early as one would want to go out in a highstorm ... not that one would want to go out, but this is about as early as it is safe to go out.
A fascinating aspect of highstorms comes at some point during the stormwall: gemstones left outside are infused with Stormlight, bringing them out of their dun state for the span of a week (or until the next highstorm).
Highstorms are more or less regular in their coming. In general, they frequent Roshar every few days, with the exception of four weeks at the end of the year known as the Weeping and at the Weeping's calendar opposite, known as the midpeace.
Highstorms have myriad effects on Roshar. They allow gemstones to be infused with Stormlight, which "fuels" most magical abilities and fabrials.
The weathering winds leave behind crumbling cliffs and jagged edges in rock formations; unprepared or ill-placed towns and cities can be decimated by a single storm. However, the seemingly desolate landscape comes to life during the riddens; the time immediately following a highstorm is when plants and animals come out of hiding to soak up the water and precious nutrients left behind by the storm. This gives an interesting insight into Roshar's plant life and creatures, which have adapted in order to not only withstand, but also thrive on the effects of the highstorm.
Though the chances of survival are minute, it is possible to weather a highstorm beneath impromptu shelters. Those who seek to use highstorms as punishment (allowing the Almighty to judge their fate) bank on the unlikelihood of their victim's survival. Caravans that are forced to weather a highstorm in the open chain their wagons to nearby boulders and use them for protection. Settlements have more permanent solutions. The city of Kholinar is built inside a large stone formation known as the windblades, while the town of Hearthstone uses the breakwall for protection.
People cannot sleep during a highstorm.
Stormwardens study highstorms and try to predict their coming. Their service is valued by Highprinces and common merchants; a list of highstorm dates can be purchased from a roving stormwarden even in the most remote locations.