Weather is rather more significant in Avalon than merely atmospheric background scenery to a location. The skies themselves are often a battleground of competing forces, including the skymasters and the thaumaturgists and those charged with the defence of the realm by priesthoods associated with the air, sky and heavens. Part of this battleground is the manipulation of already existing natural forces, like clouds and winds and stormfronts that sweep eternally west to east across the Avalon continent, blending with fronts moving south from the mountains and often colliding - effect and counter-effect - at various points about the continent. Temperature also plays a role in determining weather, as do influences from the ground: waters evaporating from lake and sea, winds swept into existence by forests acting in unison.
Type WEATHER to try to assess the weather in your location, and examine the Survival ability "survey" for a handful of commands for surveying windspeed and storm potency, etc.
Rain: it is usually important to keep yourself protected from rainfall, unless it's merely a light drizzle. An umbrella is the easiest purchase to aid you against most regular downpours: see HELP UMBRELLA. If you become overly wet you will find yourself catching a cold, or items in your inventory of fire could be doused; likewise important fires in a location may become extingushed. The effect are mostly common sense and one should avoid, if possible, using any skill requiring fire/calm weather if the cloud are full of stormclouds - whether it is raining or not. Sometimes, by natural and/or supernatural influence, the storms can become violent - torrential - and these are more harmful. Flooding can occur; animals can drown if given no refuge; gardens and fieldcrops can become ruined.
Wind: there are invariably light winds gusting about the continent as temperature shifts and weather fronts and the natural west to east flow intermingle in the skies and play out secondary effects at ground-level. Usually this is nothing to worry about. However, if the winds become extremely strong they can have a profound effect on one's surroundings. Trying to walk against a powerful gale is a slow process, while moving with too much wind behind you can gust you further than you might wish as your momentum carries you along. Storms can be whipped up to greater violence, hurricanes have numerous effects on one's personal safety and the safety of one's crops, animals, possessions and constructions.
There are two primary professions whose influence in the skies is unmatched: the loremaster and the sorcerer, specifically the skymaster and thaumaturgist branches of these professions. The ranger and the seer, from very different angles, are able to influence weather and the skies; the former from the forest, the latter from the ethereal winds. Those skilled with the influencing of the elements as a secondary ability can also wield minor power over the weather. There is the whole world of ornithology and the use of birds as loyal companions, their main theatre of operation being in the skies and thus affected by extreme weather. Riding flying steeds, like the eagle, can take any individual up into the skies - touching closer to the weather, so it is worth keeping an eye on the storm and the winds if one utilises the skies for travel about the land.
There is, therefore, a great deal to explore in weather and its consequences. It is considered a feat worth of every Avalonian's attainment, to be taken to see the Doors of the Night to watch the creation of the winds and the virgin clouds. Likewise it is worth knowing the most clearcut ways to shelter from the effects of extreme weather: keeping under cover, inside strongly built constructions, or - woodland folk permitting - one is often able to seek shelter from the elements beneath the protective shield of the forest canopy.
One inch of rain falling over a medium-sized forest would be 17.4 million gallons of water held within a single large stormcloud.
Further information on areas touched on in this little introduction can be found in: HELP SKIES, HELP LOCATION, HELP SKYMASTERS, HELP BREWING, HELP GREENWOOD, HELP LOCALE, and various helpfiles led onto from that sample smattering.