The major cause of damage to people from the weather is the effect of heat and cold. The following are rules to model the effects of extreme heat and extreme cold on various types of people. They are simple to use and seem reasonably consistent and accurate.
Each species or race has an optimal temperature range and a survivable temperature range. Within the Optimal Range, the person will not feel ill effects from the temperature. Within the Survivable Range, the person will be uncomfortable and will suffer some ill effects. Outside the Survivable Range, the person will suffer damage and will eventually die if not removed from the situation.
For every degree Celsius above or below the Optimum Temperature Range, the person will lose 1 fatigue point per hour of exposure. Such fatigue loss is not regained by simple rest, but instead is regained by resting in a temperature within the Optimum Range and will regain 1D3 -1 fatigue per hour of resting at a safe temperature.
For each degree Celsius above or below the Survivable Temperature Range, the person will lose 1D6 Fatigue Points and 1D3 - 1 general hit points per hour of exposure. Fatigue points may be regained as above, but the hit point loss must be healed by magic or by normal and natural healing.
Several factors affect the actual temperature, changing the effective temperature of the person.
Wind causes a Wind-chill Factor, reducing the effective temperature by 1 degree Celsius per 5 points of wind strength.
Fires increase the effective temperature. When outside, a fire will increase the effective temperature by 1D3 degrees Celsius per level of intensity of the fire. When indoors, a fire will increase the effective temperature by 1D3 degrees per hour, with a maximum increase of Intensity x 5 degrees.
Clothing changes the effective temperature by different amounts,
depending on the clothing in question. Most clothing increases the effective
temperature, but some protect against high temperatures.
|Clothing||Cold Protection||Warm Protection|
As an example, imagine a human wandering on Valind's Glacier wearing
blubber and fur clothing. The temperature is -45 degrees Celsius but there
is a STR 50 wind blowing. The Wind gives a Wind-chill of -10, so the effective
temperature is -45 -10 + 15 + 20 = -20. His low survivable temperature
is -15 and his low optimal temperature is 0, so for every hour he is in
these temperatures he loses 5D6 fatigue and 5D3 - 5 hit points because
he is outside the survivable temperature and 15 fatigue points because
he is outside the optimum temperature range, losing a total of 5D6 + 15
fatigue points and 5D3 - 5 hit points per hour, but what do you expect
in temperatures that would freeze flesh? If he manages to move out of the
wind, the effective temperature becomes -10, so he would only lose 10 fatigue
points per hour. If he moves into a cave and lights a medium fire, the
temperature rises by 2D3 degree per hour, with a maximum of 10 degrees,
increasing the temperature to 0 degrees which is at the edge of his optimal
range, so he can sit and wait out the storm.
|Species||Low Survivable||Low Optimal||High Optimal||High Survivable|
|Mistress Race Troll||-50||-15||15||35|
These figures may seem limited, but bear in mind that wearing clothing or using fans etc. will change the effective temperature and so extend the temperature ranges.
Various magics can also affect temperatures, several cults grant salamanders, sylphs and shades, all of which change the temperature, Warm Earth is granted by Lodril and Caladra & Aurelion and Himile grants Decrease Temperature. A well prepared person can also decrease the effects of extreme temperatures.
During my campaign, I used these rules as guidelines to what effects extreme temperatures had. I did not slavishly keep to these rules and often ignored them for minor temperature changes, but they were useful in Deserts, near Lava Pools and on Valind's Glacier and within Pools of Darkness.
Jason Brownlee has a simpler idea that could easily work. Here is his idea:
Something we've always done is assign the weather a number. For instance:
weather from 50-70 degrees is a 0. Warmer weather would be a 1,2,or a 3.
Colder weather would be a -1,-2,or a -3. When you bought clothing for cold
weather, you would for example buy a "1" cloak, which would be enough to
counteract the effects of -1 weather. Fatigue would be affected fairly
similar to the way it is affected in your system with the difference between
your clothing and the weather making the effects more or less severe.