Climate

Weather is more than just set dressing to establish mood—it has mechanical effects you can combine with environmental components to create a more memorable encounter. Weather can impose circumstance penalties on certain checks, from –1 to –4 based on severity.

Fog

Fog imposes a circumstance penalty to visual Perception checks, depending on the thickness; it causes creatures viewed through significant amounts of fog to be concealed; and it cuts off all visibility at half a mile or less—possibly much less. Conditions limiting visibility to about a mile are called mist, and those that do so to about 3 miles are called haze.

Precipitation

Precipitation includes rain as well as colder snow, sleet, and hail. Wet precipitation douses flames, and frozen precipitation can create areas of snow or ice on the ground. Drizzle or light snowfall has little mechanical effect beyond limited visibility.

Visibility

Most forms of precipitation impose circumstance penalties on visual Perception checks. Hail often is sparser but loud, instead penalizing auditory Perception checks. Especially heavy precipitation, such as a downpour of rain or heavy snow, might make creatures concealed if they’re far away.

Fatigue

Precipitation causes discomfort and fatigue. Anything heavier than drizzle or light snowfall reduces the time it takes for characters to become fatigued from overland travel to only 4 hours. Heavy precipitation can be dangerous in cold environments when characters go without protection. Soaked characters treat the temperature as one step colder (mild to severe, severe to extreme; see Temperature below).

Thunderstorms

High winds and heavy precipitation accompany many thunderstorms. There’s also a very small chance that a character might be struck by lightning during a storm. A lightning strike usually deals moderate electricity damage, or major electricity damage in a severe thunderstorm.

Temperature

Often, temperature doesn’t impose enough of a mechanical effect to worry about beyond describing the clothing the characters need to wear to be comfortable. Particularly hot and cold weather can make creatures fatigued more quickly during overland travel and can cause damage if harsh enough, as shown in the table below.

Appropriate cold-weather gear (such as the winter clothing) can negate the damage from severe cold or reduce the damage from extreme cold to that of particularly severe cold.

Temperature Effects

Category	Temperature	Fatigue	Damage
Incredible cold	-80°F or colder	2 hours	Moderate cold every minute
Extreme cold	-79°F to -21°F	4 hours	Minor cold every 10 minutes
Severe cold	-20°F to 12°F	4 hours	Minor cold every hour
Mild cold	13°F to 32°F	4 hours	None
Normal	33°F to 94°F	8 hours	None
Mild heat	95°F to 104°F	4 hours	None
Severe heat	105°F to 114°F	4 hours	Minor fire every hour
Extreme heat	115°F to 139°F	4 hours	Minor fire every 10 minutes
Incredible heat	140°F or warmer	2 hours	Moderate fire every minute

Wind

Wind imposes a circumstance penalty on auditory Perception checks depending on its strength. It also interferes with physical ranged attacks such as arrows, imposing a circumstance penalty to attack rolls involving such weapons, and potentially making attacks with them impossible in powerful windstorms. Wind snuffs out handheld flames; lanterns protect their flame from the wind, but particularly powerful winds can extinguish these as well.

Moving in Wind

Wind is difficult or greater difficult terrain when Flying. Moving in wind of sufficient strength requires a Maneuver in Flight action, and fliers are blown away on a critical failure or if they don’t succeed at a minimum of one such check each round.

Even on the ground, particularly strong winds might require a creature to succeed at an Athletics check to move, knocking the creature back and prone on a critical failure. On such checks, Small creatures typically take a –1 circumstance penalty, and Tiny creatures typically take a –2 penalty.