In my experience steam seems to cause massive scalding, much more painfull then either water or magma. This may be due to temperature transfer (turned on in my game), but it's very different from d40. I've used DFHack to try and kill with steam alone with meager success, doing it indoors seems to be the key. Can I get a verification?
Rain and snow
I have volcano at freezing biome, with a little piece of temperate biome. After massive excavations for defensive purposes, magma channel was dug to that temperate piece. Now a snowstorm produces steam at that place - I think it's because snow becomes rain there, while the frozen part doesn't steam. Anyway, it makes no obsidian. Peregarrett 13:53, 31 August 2010 (UTC)