Blowing a Hoolie

Its windy outside right now. The weather is quite rotten even by British standards, which are pretty low. The wind is gusting and rattling the roof tiles and the rain is horizontal (not a good sign). Horrible as it is, this is also a good time to be inspired when writing a game. Weather is often an invisible factor in a game, much like encumbrance and light sources in dungeons. But it can actually make a game more interesting and give a location some much needed character.

• Heatwave - Hot temperatures can make everything an effort. Layers of clothing such as leather armour can be unbearable to wear. Even at night it can be hard to get any rest reducing a characters reactions and effectiveness.
• Severe Winds -Wind is noisy, impedes movement and makes almost any action harder to perform. In severe wind its almost impossible to create a fire without shelter.
• Thunderstorm - The most obvious threat comes from lightening, especially if the characters are wearing metal armour! Lightening strikes can kill outright but even if it doesn't severe burns can be inflicted. Metal items such as jewelry can even be melted into the skin of the victim.
• Fog - Fog or Ground Mists can reduce vision to a matter of inches. Its very easy to get lost or disoriented in such conditions and of course it is near on impossible to see an ambush or hazard until your nearly on it. Even sound can be muffled by thick fog making directional hearing very difficult.
• Heavy Rain - Heavy rain reduces vision dramatically. The spray caused by heavy rain can even create a fog like effect reducing the range of effective sight to a few yards. Its also very noisy and will muffle all but the loudest sounds.
• Wind & Rain - Combined you have a miserable situation for anyone caught outside. The windchill will drop temperatures and will force freezing cold water (in temperate climates) into every part of an adventurers gear. In Tropical climates cold isn't a factor but damp clothing will rot quickly unless dried thoroughly.
• Flash Floods - Even if the sun is shining where the PC's are it might have been raining heavily somewhere else. If that was in the mountains for instance then the result can be flooding that literally comes out of nowhere with virtually no warning. That comfortable camp in the banks of a small stream might not be all that comfortable after all.
• Cold - Cold can sneak up on the players during overland treks. What might be bearable conditions during the day can deteriorate into severe cold of an evening. Night time temperatures can be anything up to 10-15°C lower than daytime temperatures. The effect on a person will depend on lots of factors such as clothing, shelter, heat sources, altitude and activity levels.
• Hail - Hail can be both noisy and painful. Usually hail is associated with ice cold rain or strong winds. Hail can be tiny but it can also be large and very painful if it hits exposed flesh. Extremely large hail can even cause serious injury to anyone not under shelter.
• Hypothermia - Prolonged exposure to cold conditions can induce hypothermia. Rain and wind can accelerate the process. The effects can be reversed but not until the characters get warm.

The weather can turn a journey to a temple or lost dungeon into an adventure in itself. Certainly crossing the wilderness unprepared will never be an option your players take again after you have hit them with a storm in the middle of the night.

(There were several spelling and grammatical errors in the original post so I have corrected and re posted.)