Have you ever been working on a map, then you start testing it, and it starts raining? Or you want it to rain, but it stops? You use the /weather clear command, but it just keeps coming back before long. Well, I used to have that problem, but have found a method to fix that. Here is a little tutorial on how to toggle among weather with infinite length with only a few command blocks.
First off, you'll need to create a new scoreboard. Run:
"/scoreboard objectives add Weather dummy"
This will create the scoreboard that we will use. Next, create a clock with repeating and chain command blocks. Remember to set the repeating one to "always active". In the command blocks, you'll need: