Wetting not recommended John. Suits are flameproof - not fireproof and not really heat proof. In a fire, you'd probably get scalded through the heat transfer. Which is why we always recommended you dried your suit between races.
For the same reason, you shouldn't really wear a watch with a metal strap. Having said that, the risk of fire is relatively slim, based on the number of races most of us have attended over the years, despite the new rules with underwear and balaclavas etc. But, it is still a risk, no matter how small that risk is - but then so is being hit in the face by a wayward bird when driving a single seater.