I was building a giant structure in the middle of a desert. It was also surrounded by a nice body of water, I build a dock for boats and whatnot. I pause my game to make me some food, about 20 minutes later, waters covered in ice and my structure is covered in snow. I basically want a plugin that either removes these blocks right away or doesn't allow them to be placed.
Try the commands /thaw in WorldEdit by sk89q. It removes snow and ice in an area that you can define. You can also simulate Snow Cover by using /snow.
go to the GetPlugins link and search for "noice". I use WeatherRestrictions to modify the weather on my world. It is supposed to also control snow and ice accumulation, too. I don't use that feature, but I can tell you that the rest of the plugin works really well.