Hammy makes some interesting points about temperature underground; one thing I've noticed is how this can affect the conditions. In summer relatively warm, moist air seems to go underground with concomitant condensation of water vapour onto relatively cold cave surfaces, while in winter the opposite happens and cave passage tend to dry out.
So the first time I went down Mistral was in the middle of a very cold spell, and the entrance crawl was quite pleasant - dry and sandy. The next time it was in the middle of warm summer weather, and the crawl was grotty and soggy.
Similarly, the traverses in Juniper Gulf are easier and more pleasnt in winter than in summer, while the 'dry' passages in the high-level route in Lancaster Hole can also vary remarkably. In a cold dry spell (such as we experienced last December) they're bone dry and easy to walk in, but in summer they can become quite slick - especially in the vicinity of Scylla and Caharybdis, where 'warm' moist air can rise from the river below. I remember on one occasion (mid-summer), when it was hard to keep one's footing all the way from Fall Pot to the Minarets on account of the condensed moisture (and where there was any non-level floor it was virtually impossible to stand up).
Anyway, Swampy, have you decided yet what you're going to do?
