Weather has been with us since the dawn of gaming to enrich the worlds we are playing in.
Rain, snow, wind, fog or sunshine brings unparalleled atmosphere to gaming.
As technology is moving forward weather is also used for more than just atmospheric effect. Racing games have started using it to add challenge to the driving experience and other genres are also using it as a challenge or gameplay mechanic.
Sadly, simulating effects such as rain in a game is harder than one might think. Developers often fail with either the effect itself, making it look ugly, or the sound of it. The sound of rain can be atmospheric or downright annoying if done wrong.
Weather effects is also notorious for slowing down your framerate and being a big system hog if programmed wrong into the engine itself.
Also not to forget. Weather in the real world have a big tendency to actually decide our gaming habits. A rainy day might drive you inside to complete that game you´ve been playing and a big thunderstorm might knock the power out in your area and instead prevent you from playing what you want. Real life weather is an aspect of gaming that we often neglect.
There are many examples of games that would never have been what they are today without the addition of weather effects. The Silent Hill games would not have worked without its signature fog, the introduction sequence to Zelda: A Link To The Past would never have gone down in history if it wasn't taking place during that particular rainy night. RPGs such as Morrowind or even the slightly older Baldurs Gate made a big deal about dynamic weather changes.
The most impressive early example of dynamic weather was in Shenmue, which realistically simulated the weather exactly as they had actually occured in Yokosuka during 1986-1987. The weather would change throughout the day, while the environments and NPCs changed their appearance and behaviour based on the weather.
In the first DLC to Fable II the hero is tasked with solving the weather problems of Knothole Island and the open world racing experience FUEL throws barns and cars at you on the track with tornadoes. Blizzard felt that weather was important enough to patch in excellent weather simulation in World of Warcraft a while after its release. Persona 4 has integrated rain into its core gameplay mechanics and a rainy day will alter the way you need to play the game that day. The best looking raindrops can arguably be found in Heavy Rain. With a title like that it better look good.
Weather effects are constantly evolving and some day they might reach the same fidelity as the rest of the graphics in the generations of hardware to come.