Make rainfall a biome-by-biome chance, instead of global.
In other words, some biomes are marked as wetter/rainier than others. But right now, it's either on or off, or desert.
I'd like to see something make rainforests almost constant rain, plains much less, and the drier areas even less than that.
My idea for this takes note that currently, rainfall on a server is server-wide and counts ALL players in a dimension for humidity value. I'd love to do biome-by-biome rain, taking into account the average frequency or cycle of a real-world biome as well as if nearby loaded biomes are raining or about to be raining. For example, a rain forest tends to rain almost every day like clockwork, but it doesn't necessarily last long (some even rain twice a day). Forests rain more than plains, since trees release vapor into the atmosphere which seeds the clouds above them, encouraging more rain there. Plains rain only occasionally, and the rains tend to be more intense because there's more room for the wind to collect heat energy from the ground. Taiga tends toward drier, so the main difference between taiga and cold taiga in-game is the humidity. Meanwhile frozen biomes tend to be very dry (the cold drives water out of the air), so they snow rarely; but again, if they're gonna snow, the weather tends to be intense. Deserts don't tend to rain except a few times a season, and those are usually HUGE gully-washer thunderstorms.
Now if you combine that with, say, a seasonal cycle, you get snow in the temperate biomes, more often near cold biomes but not near hot biomes. And so on. Rains are more intense during certain seasons, and so on.
Suffice to say, the math isn't difficult since it's mostly consulting a chart every minute and adding a biome-based, time-based value to the humidity of loaded chunks (pre-dawn hour, day, evening hour, night). Once humidity goes over 100%, it rains and humidity gradually drops to a biome-based minimum at a biome-determined rate. If it's raining in a nearby biome, humidity increases faster. If in or near a desert, humidity decreases except when a thunderstorm happens. Thunderstorms have a base 2% chance of happening once it starts to rain, varying based on biome and season, and add +100% to humidity but decrease it faster. If it's thunderstorming nearby, the chance of a thunderstorm goes up to 50%, more if it's already raining.
This approach would lag somewhat like old versions of Thaumcraft, which constantly updated the vis values of each loaded chunk instead of having aura nodes to localize vis, but on the other hand, no more raining just because someone else was online today, and no more rain EVERYWHERE just because it started raining at your house or active base. It would also add a more visible variety to how often and how long it rains.
And just for fun, you could change the color of the sky by visual overlay in morning and evening (redder or bluer) depending on how humid the air is.
"Red sky at morning, sailor take warning; red sky at night, sailor's delight."
