It looks like client does the setOvercast transition much slower than the server.
Manual weather overrides are set in the mission.sqm settings.

300 SetOvercast 1

Executed on the server and client is still at 0.661669 while the server is already at 0.895198 overcast.
Looks like something is going wrong here, I tested the other weather commands, looks like its only setOvercast that behaves like that.
This will cause different weather for clients that join after that was executed compared to clients that were already online.
For example in connection with lightnings (they do appear only if overcast >= 0.90), so one client could have lightnings and thunderstrikes and the other not (due to overcast value difference).

Also, when you execute this on the server, the server changes the overcast value instantly (like intended) but the client does its normal transition instead of also switching instantly.
Is this intended or a bug ?

0 setOvercast 1;