The Weather Underground are a radical group of leftist hippies who tried to control the weather back in the 1960's. They would have disbanded after they failed to do anything worthwhile, but they were too high to break up the party.
Nowadays, they use their intricate network of satellites to spy on Good Americans™, but claim they are doing something about the declining barometric pressure and make up lies about other things they are not qualified to speak about.
During the 1960's there was no terrorist organization involved in more terrorist activities than the Weather Underground. Here is just a partial list of the things they did against innocent Americans:
They are also believed responsible for the hit Disco single It's Raining Men, though that may have been the Weather Girls.