What kind of weather do your characters like best?
It might not be personal at all. It might depend on what they’re up to. Most legal activities are great with clear and dry weather. However, if you’re sneaking – and even if you’re a good guy, maybe especially if, you will be sneaking – you might need the cover of darkness or bad weather.
Which has its pros and cons. On the upside for anyone trying to be sneaky, bad weather is often noisy weather, covering any stray sounds of people being where they shouldn’t. It also tends to lower watchers’ guards, due to the bedrock conviction of “nobody sane would be out in this”. (Whether or not your characters are sane is probably up for debate.)
Downsides? Nasty weather means that unless you’re careful, you’re likely to leave signs someone was there. Blown snow, wet footsteps, even a breeze from an opened window might be enough clue for an alert opponent to know the game’s afoot.
Now, what weather you may want as a writer is a whole ‘nother consideration. Because it gives your story atmosphere! Ominous aspects, hints of the supernatural, an aura of mystery; murder and assassinations in broad daylight just don’t seem right. (Though historically, it happens.) The cover of night, a flashing thunderstorm, lightning casting unpredictable monstrous shadows – these add to the feeling of being hunted, of predator and prey… murderer and victim.
If you’re not really worried about big thematic Drama with your weather, at least think of the little details. Weather makes a difference in many things, any of which might apply to your story. Sensory input is a big one; smells, white noise, visual distraction. How and if animals seek shelter; see snakes in your sleeping bag. Cold and warm spells will affect the quality of pelts and hides, what herbs can be found, what’s in season in the marketplace. Snow and ice make foraging for water harder; either breaking ice or gathering huge amounts of snow to melt into a little water. Weather will affect where animals choose to live; wolverines for one are found in areas where there are deep snows in winter, trapping prey to feed on and preserving frozen carrion. Unless you’re in a completely climate-controlled dome, weather affects what most people are doing. Particularly farmers and crafters; a coat of varnish or paint done in high humidity will never dry completely, always turning tacky when it’s moist again. And if you showed your farmers out cutting hay for winter fodder, and then a storm comes up? You should have angry, maybe desperate people on the loose, and possibly accusations of weather-witching!
Take some time to watch the skies, as well as the weather channel. As they say, into every life, a little rain must fall. Think how you want your characters to deal with it!