[clarencecuzz]

Or...

pawn Код:

public OnGameModeInit() //Or OnFilterScriptInit for filterscripts
{
    SetTimer("WeatherChange", 3600000, true);
    return 1;
}

forward WeatherChange();
public WeatherChange()
{
    new rand = random(45);
    SetWeather(rand);
    return 1;
}

Simple.