Well if at any point you see the flesh literally turning to goo, you can probably be assured it's done for, I've had soft corals tolerate temperatures of 90F for quite a few hours and still come back, yeah they were majorly PO'd but they survived.
Good thing about soft corals is that they grow very fast and I'm sure someone in the area would be more than happy to give you a few frags to help you out after the heat wave passes if you do have any die off.