Severe Thunderstorm

The combined effects of torrential precipitation and high wind reduce visibility to zero, all perception checks and all ranged weapon attacks impossible.

Unprotected flames are automatically extinguished, and protected flames have a 75% chance of being doused.

Creatures must succeed on a DC 18 Strength save or be blown away (Small or smaller creatures; knocked prone and rolled 1d4 x 10 feet, taking 1d4 damage per 10 feet), knocked down (Medium; prone), or checked (Large or Huge; unable to move forward against the force of the wind).

Airborne creatures are instead blown back 2d6 x 10 feet and dealt 2d6 damage due to battering and buffeting (Medium or smaller creatures), blown back 1d6 x 10 feet (Large), or blown back 1d6 x 5 feet (Huge or Gargantuan).

In addition, thunderstorms are accompanied by lightning that can pose a hazard to characters without 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. Each bolt causes electricity damage equal to 1d10d8 dice.