Outdoor units have Ingress Protection (IP) ratings written on the specs. Commonly, they're IP X4, which implies that the unit is protected from water sprays from any direction.

This rating is only applicable if the chassis cover/flaps/seals and all screws are intact. What happens usually is that technicians who work on these units, whether to fix or clean it, neglects to put back everything together properly. Oftentimes, this invalidates the IP rating.