Spigot 1.13.1 latest
EssentialsX 2.15.0.45
Command syntax is

weather storm|sun duration

Spigot 1.12.2
EssentialsX 2.15.0.17
Command syntax was

weather world storm|sun duration

The current syntax generates an error in 2.15.0.17

Error: World named storm not found!

This change breaks a pretty important part of my world weather control. Please return the previous syntax.

PEBKAC. /weather was hijacked by another plugin.

Always use specific command form in skripts and etc:

plugin:command