Does the rain gauge empty automatically?

Yes the 5-in-1 rain gauge does have a self emptying collector cup and will empty each time the tipping cups inside rock back and forth. Regarding when a rainfall event ends your current rain event will clear when no rain registers for 8 hours OR no rain registers for 1 hour and barometric pressure rises by .03inhg or more.

If no rain has been registered for 8 hours the gauge starts the rainfall event measurements again.