Fact that everyone imagine other weather in RP is causing problems, really ...
So, I we will use 'Attention Message' for announcing weather. (those messages that show under Navbar)
I'd make some images for weather ... and then I'll just add new message to scroll with others. Since message about weather will be picture, it'll be more visible.
All measage will be like ... (for ex.)
Season: Winter
Temperature: -10 C / (someone need to help me change it to F)
Weather: Slight, cold wind. It may snow during day.
and all of it on top of picture showing this weather.
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I'll change weather about once a week, or more often if I'll feel like it ...
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Don't make up your own weather in RP.