Weather is a feature that was introduced following the updated version 2.5 and newer versions. It was a winning suggestion on the WolfQuest ideas thread. 
Additions as of 2.5 include:
Additionally, weather has its effects on prey scent trails and sometimes even the behavior of prey such as elk. It is possible to disable the weather effects through game settings/options using the weather toggle. Players cannot modify or decide the game's weather, which changes in random intervals.
During January 2011, a fundraising contest was held to decide whether or not lightning would be added to the game. By March 1st, 2011, the contest ended and $1,181 was raised, successfully reaching the target and securing the new feature in 2.5.
Lightning has a chance of striking a random tree near the player and setting it ablaze. It is not currently possible for players, their mate or their pups to be struck or killed by lightning. Similarly, predators are unaffected by weather conditions.