I had it happen in an A330 while parked on a remote bay at Jeddah in the middle of summer with Flaps 1 set and the OAT at 50°C. The APU bleed valve automatically closed (by design), depriving us of any air conditioning. The engineer tried to use ground carts to blow cold air onto the wings, but couldn't get rid of the ECAM caution. He ended up having to de-power the aircraft to reset the system and restore the APU air. Fun times (not)!
Doesn't seem to be an issue on the A350.