Weather

Bad weather frequently slows or halts travel and makes it virtually impossible to navigate from one spot to another. Torrential downpours and blizzards obscure vision as effectively as dense fog. Most precipitation is rain, but in cold conditions it can manifest as snow, sleet, or hail. If the temperature drops from above freezing to 32° F or below, it might produce ice.

The combined effects of precipitation (or dust) and wind that accompany storms reduce visibility ranges by three-quarters, imposing a –8 penalty to Perception checks. Storms make aiming with ranged weapons difficult, imposing a –2 penalty to attack rolls, and archaic ranged weapons can’t be fired at all. Storms automatically extinguish unprotected flames. Storms commonly appear in three types: dust, snow, or thunder.

Whether in the form of a low-lying cloud or a mist rising from the ground, fog obscures all sight beyond 5 feet, including darkvision. Creatures 5 feet away have concealment (20% miss chance).

Wind can create a stinging spray of dust, sand, or water, fan a large fire, rock an atmospheric transport midflight, and blow gases or vapors away. If powerful enough, it can even interfere with some ranged attacks and knock characters down. Below are the most common wind forces seen on habitable worlds.