A sandfire storm was a type of storm that occurred in Vulcan deserts. These storms advanced at high speeds and were characterized by strong winds and blinding sand, as well as lightning-like discharges of electricity close to the ground. Sandfire storms could last from hours to days, during which travelers must seek shelter in a sealed space.
In 2154, Captain Jonathan Archer, Commander T'Pol, and Syrran were caught in a sandfire storm in Vulcan's Forge. They took shelter in a cave, but Syrran was killed by an electrical strike. (ENT: "The Forge")
The idea of sandfire storms was based on storms that are thought to exist on Mars. The name "sandfire storm" was thought up by André Bormanis. ("The Forge" audio commentary, ENT Season 4 Blu-ray)
In the script of "The Forge", a sandfire storm was described as "a wall of roiling sand [which] has sprung up, billowing forward, lit from within by enormous flashes of lightning."
According to DVD text commentary for "The Forge", sandfire storms are created by static electricity generated when sand particles rub together in a windstorm.
A sandfire storm in Vulcan's Forge
Archer and T'Pol run from a sandfire storm