Seasonal Weather

A mod that adds seasonal weather to the game.

Features

Adds meteorological seasons to the game. The global temperature will rise and fall according to the seasons.

With the existing values in worldglobal.xml, each season is three in game weeks long (so, it takes 84 in-game days to get through all four seasons). The game starts in the middle of the Spring season. The temperature variation is 31 degrees Fahrenheit, which is taken from hard-coded values in TFP code.

This is all customizable; see below.

Customizing

All these things are customizable in worldglobal.xml:

Length of the seasonal year (in game days)
Temperature variation (range)
Starting season

But there are some caveats:

The seasonal year does not start until after a “weather grace period.” The grace period is hard-coded in the game (and is not related to the “newbie coat” buff).
The global temperature cannot go over 101 degrees, or below 70 degrees (Fahrenheit). These limits are hard-coded, and result in a temperature variation of 31 degrees. You can specify a variation higher than this, but it will mean that you hit the limits sooner in each season, and the temperatures swing between these limits faster. (If it helps, think of it like clipping in digital audio.)
When a starting season is specified, players start in the middle of that season. Khzmusik chose this because he think it’s what most people expect. So, if you choose spring (the default), you’re starting at the median global temperature, and it goes up as you enter into summer.