I would think that the RC/PRO CAN be held at least partially liabile for incidents as a result of starting races in extreme weather.

I am not an attorney, but part of the PRO's responsibility should be to have a rough idea of the design and performance envelopes for the vessels in the regatta. If the OBSERVED weather conditions are beyond that envelope, it could be considered negligence on the part of the PRO to start or continue a race.

Would it be a good idea to start a race when lightning is striking all around? Most likely not... Why? Because you are posing an undue risk to the participants...

Would it be smart to start a race when it is blowing well over 20 kts, knowing that most of the boats aren't designed for that kind of wind? I know most sailors could handle it, but what if there were an accident and injury?

Could the prosecuting attorney argue that the PRO should have known the conditions were dangerous and postponed the race? Would the PRO have expected a greater than average chance for boat damage and/or participant injury? I would think this may have traction to a jury...

That being said, I still think it's the skipper's primary responsibility to ensure the safety of the vessel and crew.