Large explosive volcanic eruptions eject water vapor and can cause acid rain.
The concentrations of different volcanic gases can vary considerably from one volcano to the next. Water vapor is typically the most abundant volcanic gas, followed by carbon dioxide and sulfur dioxide. Other principal volcanic gases include hydrogen sulfide, hydrogen chloride, and hydrogen fluoride... Large, explosive volcanic eruptions inject water vapor (H2O), carbon dioxide (CO2), sulfur dioxide (SO2), hydrogen chloride (HCl), hydrogen fluoride (HF) and ash (pulverized rock and pumice) into the stratosphere to heights of 16-32 kilometres (10-20 mi) above the Earth's surface. The most significant impacts from these injections come from the conversion of sulfur dioxide to sulfuric acid (H2SO4), which condenses rapidly in the stratosphere to form fine sulfate aerosols...
Wikipedia, Volcano, 2019
Besides pulverized rock and pumice, volcanic ejecta contain water vapor that forms rain or acid rain.
However this was portrayed in the Quran 1400 years before it was discovered. In the story of Lot, a volcano showered them with pumice and rain.
[Quran 15:74] And We turned it upside down, and rained down upon them stones of pumice.
[Quran 26:173] And We rained down on them a rain. Dreadful is the rain of those forewarned.
Today we know why that rain was dreadful; it was acid rain.
How could an illiterate man who lived 1400 years ago have known that volcanoes can cause dreadful rain?