Jared Neil

Note that as of the command re-write for 1.13, 0 is now a valid value for the duration. This allows /weather clear 0, which mimics the effects of sleeping in a bed. Whereas in 1.12.2 there was no way to perfectly simulate sleeping (the closest thing being /weather rain 1.

I think it's important to be able to simulate sleep, and I think both of the aforementioned commands are quite unintuitive. The ideal would be that /weather clear with no duration actually mimics sleeping exactly, which, as of now, is definitely not the case.

As of 18w15a, /weather clear will clear the weather for exactly 6000 ticks (5 minutes), at which point a thunder storm begins.
If the default is changed to 0, instead of 6000, then /weather clear will have the same effect as sleeping in a bed.

After further thought, this seems like it might be the correct behavior. If you think of @s as referencing the command execution context, then this is working correctly. If you think of @s as re-selecting the same entity that is executing the command, then this seems broken. Now that the former idea is also in my head, it definitely seems like the correct way of thinking about @s.