We're in Britain and can get wet, people also play in Canada in all weathers.
Prepare and plan appropriately for the weather and its all fine.
A bit of rain will have no impact.
More rain can mean thinking about it:
Look after your paint - no matter the weather don't open every bag straight away. Open one bag at a time and pod up.
If you have a speedfeed get the normal lid back on, (if you fitted a speedfeed you of course did keep an eye on the lid and spring etc, keeping them in your gearbag.
If you have a barrel insert set etc then take into account that the size of the balls may vary more during the day from moisture in the atmosphere.
Some people may cover up the porting in the barrel.
Ignore 'rain covers'. They are a euphamism for suppressors in the US.
If your gun is decently maintained, and you close the grip properly your circuit boards and batteries will stay dry unless in a major storm or under water.
Have spare dry / clean / warm clothes to go home in, have spare clothes to play in if palying over time in bad weather.