First is more a question, why have we lost the weather station? Real life F1 teams are able to have some idea what weather is coming..
But my suggestions goes as follows. I know I find it a pain that you don't even know its started raining half the time till your in the pits... possibly putting the wrong wet tyres on, too little fuel etc.
If a person is live racing could it start to rain maybe this could trigger a pop up, something VERY OBVIOUS, !! WARNING RAIN !!. If this box could then include the pit stop controls. Tyre choice, fuel and very important... a cancel button?
Was in a mix weather race the other night, weather and tyre requirements changed 3 times, found it so almost impossible to manage the race effectively.