Weather

Weather is something that it's easy to overlook in game. Partially because it's one of those background things, but also because it can be a pain to manage weather in a game.

Despite being a d6 system, I'm a fan of some things being managed by other dice. Enter the d20 guide to weather.

1-70%: Normal weather for season.
71-80% Abnormal temperature (50/50 to be a heat wave or cold snap- 10 degree difference in normal temperature. Cold areas are 70% likely to be a cold snap, hot are 70% likely to have a heat wave).
81%-90% Inclement Weather (precipitation, such as snow or rain, or severe winds in deserts)
91%-99% Storm (heavy rains, snow storm, dust storm)
100%- Powerful Storm (tornado, hurricane, blizzard, windstorm)


Effects on weather: (Visibility modifiers may apply to special visions and hearing as well)

Abnormal Temperature: Characters not dressed "for the weather" may take a +1 TN penalty to physical checks as the temperature bothers them.

Inclement Weather: Rain, snow, and desert winds can provide visibility modifier of +1, and can cause a +1 TN modifier to drive checks (particularly to handling scores of vehicles).

Storm: A storm can apply a +4 visibility modifier as well as driving TNs. Movement (even vehicles) should be at 1/2 speed.

Powerful Storms: These can cause random debris to fly around, possibly hitting people. Power can easily go out. Visibility should be effectively blind (+7 visibility modifer), and drive checks are at +8 or more. Natural flight (such as for birds or fairys) should be impossible. The visibility modifiers likely apply to hearing checks also, and certainly apply to all "special" visions, like ultrasound and thermovision.