Volcanoes produce their own weather systems. Dust and ash emission into the atmosphere seeds clouds, producing high rainfall at many active volcanoes Rain mixes with sulphur dioxide to produce acid rain.
The groundwater table at the summit area of volcanoes is
usually much deeper than at their slope, because of the abundance of water-permeable material. Volatiles from underlying magma rise up
to a geothermal area or directly to vent systems. Volcanic gases and fluids penetrate aquifers on their way to the surface.
Periods of heavy rainfall have been associated with increase eruptive activity at volcanoes, due to phreatic explosions.