In the weather section of the tick function there are 6 variable allocations.
The first one is a variable you get from a function that decides if it’s raining or not from rain gradient (the sky colour, but more later on this). The other variables are clearWeatherTime, rainTime, thunderTime, isRaining and isThundering from the world properties.
The first part of the code is an if block that checks if clearWeatherTime is bigger than 0. This part is basically a hackfix to make it so that the weather will stay clear for a certain amount of time when the /weather clear [time] command is used. In this block clearWeatherTime will count down. After this thunderTime and rainTime will be set to 1 if it’s not thundering or raining respectively. If it is thundering or raining they will be set to 0. After this thundering and raining will be set to false in the properties.
What this accomplishes will be that once clearWeatherTime has reached 0, it will start raining and thundering the next tick.
clearWeatherTime isn’t bigger than 0, thunderTime and rainTime will be checked.thunderTime is bigger than 0 we’ll check if thunderTime - 1 is equal to 0. If that is the case, then thundering will be reversed. This means if it was thundering, it will stop thundering and if it wasn’t thundering it will start thundering.thunderTime isn’t bigger than 0, a new value is set for thunder time.This value is decided by:
thunderTime = thundering ? this.random.nextInt(12000) + 3600 : this.random.nextInt(168000) + 12000;
In a more readable format, this will mean that:
thunderTime will be between 3 600 and 15 600.thunderTime will be between 12 000 and 180 000.Which value somewhere in this range it becomes is determined by a random factor.
The same process happens for rainTime, though the new value for rainTime is determined differently:
rainTime = propertiesRaining ? this.random.nextInt(12000) + 12000 : this.random.nextInt(168000) + 12000;
In a more readable format, this will mean that:
rainTime will be between 12 000 and 24 000.rainTime will be between 12 000 and 180 000.Which value somewhere in this range it becomes is determined by a random factor.
After this the values that were changed will be reallocated to the corresponding fields.
So now for the explanation of how this actually works. The way in which this works is a little confusing.
clearWeatherTime isn’t used to determine how long the weather will stay clear outside of commands. Instead what happens is:
The game starts and clearWeatherTime, rainTime and thunderTime are set to 0. raining and thundering are set to false. Now, since everything is set to 0 it will immediately go to the part where it sets the timers, using the formulas we’ve just seen. In this case rainTime and thunderTime will be used to indicate how long it will not be raining or thundering. Both timers will count down, and only when they have reached 0 it will start raining or thundering, depending on which timer ran out. It will start this weather by flipping the boolean as we’ve seen before. After this a new time will be set for rainTime or thunderTime. This time, they’ll be used to indicate how long it will be raining or thundering. By constantly flipping the time rainTime and thunderTime represent, there’s no need to use clearWeatherTime. Thus we only have a value for this if we want to force the game to keep the weather clear for a certain amount of time no matter what.
A whole separate part of the weather are rain and thunder gradients. These gradients are used to determine the ambientLightLevel and the colour of the sky. As you know the sky darkens when it starts to rain or thunder and brightens again when the weather becomes clear. Well these gradients will take care of that.
When the weather is clear, both gradients will be 0. The value for these gradients will always be between 0 and 1 inclusive. If it gets higher than 1 it will be set back to 1. If it gets lower than 0 it will be set back to 0. Each tick the following happens. If it is raining, each tick we’ll add 0.01 to the rain gradient. If it’s not raining we’ll subtract 0.01. This way when the sky will take 100 ticks or 5 seconds to change colour completely.
Now there is a isRaining and isThundering method, boh will determine if it’s raining or not via the gradient. These functions are used to determine the weather outside of the tick loop.
Rain will only begin to fall when the gradient is bigger than 0.2 and will only stop falling when it’s smaller than 0.2 again. In this case we’re speaking visually of course. Internally the properties are already set when the gradients start changing.
First the time of day will be set to morning if a player has just finished sleeping. It will also reset the weather if the weather cycle is enabled. Resetting the weather set rainTime and thunderTime to 0 and raining and thundering to false.
If daylight cycle is enabled, the world time will be increased by one & the time of day will change.
Lightning strikes don’t happen in this part of the tick but rather in the chunk part. See Game Tick for more info.