On the whole, weather doesn't play a huge part in fantasy. Oh, there's extreme weather, needless to say, whether it's blizzards, floods, or the baking heat of the desert (or just that Winter is coming to Westeros) but otherwise most fantasy (including mine, I admit) seems to take place in generic conditions of a pleasant day in late spring or early summer. It doesn't drizzle just because it can.
That is, of course, an exaggeration. This piece came largely from reading Joe Abercrombie's The Blade Itself, in which the weather makes itself felt in a variety of realistic ways, emphasising the contrast with other stories, and I'm sure there are other examples I don't know. Some other authors I'm familiar with, both published and unpublished, build the climate into their work, though again that often comes in broad strokes, such as a monsoon.
Perhaps the relative lack of more intimate weather comes from the understandable desire of authors, not to mention their readers, to concentrate on important elements of the story, rather than waste time on irrelevant background, or even a desire to make the fantasy world less grey and dull than the real one. We want to see Ug the Barbarian's sword triumph over the Evil Overlord's henchmen and allow him to rescue his True Love. We don't particularly want to see him getting soaked to the skin while he's doing it.
Like other writers, I've used plenty of extreme weather. My characters have struggled through arctic conditions and through the searing heat of deserts; I've had storms a plenty, and I've had irresponsible sorcerers trying to stop a monsoon, with disastrous consequences. And yes, I think it has even rained normally on occasion, though not often enough.
Nevertheless, even a normal range of weather can create dramatic situations. The rain might get into the supplies and spoil them, leaving our band of heroes short of food. Wind and wet might prevent them from lighting a fire * (unless one of them happens to keep a fire elemental as a pet) with all kinds of consequences. Poor visibility might prevent them from seeing the band of orcs waiting to ambush them. Conditions might persuade them to seek refuge somewhere they really shouldn't ("Let's shelter in that nice, dry cave" being roughly equivalent to "I'll just check the cellar — there's nothing to worry about"). Or the weather might affect their health and reduce their effectiveness.
None of these drawbacks would be appropriate for superheroes who can trek for sixty miles a day and take on twenty swordsmen without breaking sweat. If you're going for something a little more realistic, though (and just because it's fantasy doesn't mean it can't be realistic too), the weather can be a powerful weapon in your arsenal.
Weather has been very much in the news in recent months, what with unprecedented snow and ice in North America and storms and floods in Europe. That's all extreme weather, though, and the everyday variety has its place, too.
Maybe, when two fantasy writers meet, at least some of their talk should be of the weather. Certainly, more of my characters will be getting wet, cold and miserable in future. Won't they love me?
* The rain in the Shire falls mainly on the fire.