I request a simple plugin to select a region where some it will snow or rain or thunder storm etc.... Its just like this one here: http://forums.bukkit.org/threads/mech-regional-weather-1-0-weather-in-regions-1060.16473/ Only then updated....
It won't be possible with snow however, because whether it's snowing or raining is biome based and calculated in the client.
I think with rain it would work though by simply only telling the client that there's weather when the player is in a certain region. However, it would look at if it was raining everywhere for the player until he leaves the region.