Weather Generator

(Feature not available in Player Genie)

Use this window to create realistic weather for your campaign. You can generate an infinite variety of weather for various locations. When you generate weather, it is automatically saved so that the next time you run DM Genie, the weather will remain consistent. Weather is always generated for an entire year at a time, starting at the current date.

Principles of Generation

The Weather Generator utilizes a set of algorithms designed to simulate real weather and real weather systems. First, the average temperature for a type of climate is taken from climate data of various locations on Earth. This is adjusted for terrain (inland regions have greater daily and yearly variations of temperature, coastal regions have less). Then, each climate has its specific weather patterns – which are generated randomly. The frequency and intensity of events is adjusted for the type of terrain – the coast will be rainier, inland regions will have more variable weather.

Each weather system generates its own type of weather for a certain amount of time. Fronts are short-period events, while in a monsoon a depression system can remain for many days or even weeks. Temperature, cloud types, winds and precipitation is determined on an hour-per-hour basis. Severe weather such as thunderstorms or tornadoes is also generated. The frequency of such events can be adjusted (see below)

Choosing a Climate and Terrain

If your campaign world is similar to earth, try to draw comparisons to locations you know. Most of North America is temperate – the center states are inland, while the western states (past the Rockies) are coastal. The east coast is more average, because the wind blows eastward, so the coast does not regulate temperature. High hills, average mountains are Mountain, while tall mountains are High mountain. Rainforests, like in Brazil, and tropical islands are usually Equatorial. Areas with summer monsoons like India are Tropical (summer monsoon). The Mediterranean is Subtropical winter rain. Dry and hot areas are Subtropical deserts (like the Sahara). Cold areas with sparse vegetation, like Siberia, are Subpolar. Finally, the North Pole or Antarctica are High polar.


Enter a latitude that corresponds to the player's current location. If you do not know, the value automatically entered when you selected the climate will work fine. This affects the length of a day. (See the Timekeeping Window ).

North/South: If you select south, winter will come in June and July while summer will be in January. The weather is not affected otherwise.

Weather Adjustment

Change the values in the text boxes. Press “Generate Weather” again to see the changes.

-          Temperature: you can increase or decrease the overall temperature by a certain number of degrees.

-          Precipitation: affects the number and intensity of rainy weather systems.

-          Variability: this modifies the daily and yearly temperature variations.

-          Severe Weather: thunderstorms, tornadoes, hail and hurricanes will come more frequently if you increase this number. This is a sure way to add some excitement to a dull ocean voyage!

-          Windiness: Simply multiplies the speed of wind by the value specified.

The time of year at which winter starts is given by the date of the winter solstice. To change it, edit the CALENDAR.TXT file. See the Timekeeping Window for more information about the calendar.

Weather Summary Graphic

This shows temperatures (the line is drawn from the daily minimum to the maximum) and precipitation (red lines) during the year. Click on it to zoom to a day.

Daily Weather

A summary of weather for each day is displayed, including min/max temperatures, cloudiness, the worst precipitation received during the day and average wind speed. Some days may receive only light rain for one hour, but that is still what is displayed in the daily weather summary.

Hourly Weather

For each hour of the day, the temperature, cloud cover, precipitation and wind speed are displayed. The weather system that is affecting the weather is also displayed.

Saving Your Weather

You can save the weather data generated to a .Weather file with the File->Save As menu item. The File->Save menu item will save to the campaign's default weather file. You can open an old weather file with the File->Open menu item. This way, if your PCs travel from one region to another, you can create 2 weather files and open the correct one depending on the PCs' current location.

Documentation for DM Genie and Player Genie, page Weather. Copyright © Mad Scientist Studios, 2006.
Help Contents   |   DM Genie home page
Click here if you cannot see the table of contents on the left