Thunderstorm
In addition to wind and precipitation, a thunderstorm is accompanied by lightning that can pose a hazard to characters who don’t have proper shelter (especially those in metal armor). As a rule of thumb, assume one bolt per minute for a 1-hour period at the center of the storm (GM rolls to hit). Each bolt deals between 4d8 and 10d8 electricity damage. One in 10 thunderstorms is accompanied by a tornado.
Source
Core Rulebook pg. 399