On Saturn a raging storm has developed from a small spot to cover an area about 4 billion square kilometres, or eight times the surface of the Earth (NASA, New Scientist).
Neptune's moon Triton has a thin atmosphere and huge streaks of black material across its surface. These are created by geysers of dust and nitrogen erupting from under its icy surface as it is heated by the sun. In other words, even at the edge of the solar system, where temperatures are below -200C, sunlight can still drive distinctive weather systems. (Carl Murray of UCL quoted in Guardian report)