In reply to Tim Chappell: Two examples spring to mind:
1) In a resort called Limone Piemonte (the second most obscure Italian resort I have ever skiied at), at the furthest point of the resort one afternoon, it started raining. Hard. The return to the resort centre consisted of miserable wet lift rides, including some of the slowest chairlifts ever built by man, interspersed with miserable sort-of skiing on a surface resembling a Slush Puppie on a slope.
2) One morning in Courchevel when the temperature was several degrees below freezing we set off down what we remembered as having been a fun mogul run from a couple of days before. Unbeknown to us, the previous afternoon the slope had been warmed up in the full sun and had got carved up in to huge, shin-high ruts. Which then, of course, had frozen rock-hard overnight. It was like trying to ski on a white water rapid that had suddenly turned to ice, like the waterfall in "The Singing Ringing Tree".
Compared to those two experiences, the white-out/blizzard/blowing a gale/combination of all three which I have also experienced from time to time has provided relatively enjoyable skiing. Particularly entertaining is when the clag clears momentarily to reveal a piste marker pole, and you realise that you have actually been skiing ever so slowly
backwards for the past thirty seconds or so because your visual frame of reference had completely collapsed. At least that's quite funny!