Precipitation was any liquid or frozen water that would form in the atmosphere and fall back to the Earth.
In 2366, while the away team investigated the source of a distress call that had been intercepted on Galorndon Core, Commander Riker asked Lieutenant Worf if his view was any better, to which Worf responded, "Not too bad, Commander. A lot of charged-particle precipitation, but I can compensate." (TNG: "The Enemy")