Scientists may have uncovered the cause of a strange “milky rain” that fell on large parts of Oregon and Eastern Washington state last week. The unusual rainfall left a powdery residue on cars and windows, as well as a lot of concerned residents who wondered what it was and where it came from. Reuters reports that meteorologists now think the strange precipitation is the result of dust storms happening hundreds of miles away in Nevada.

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“We’re fairly certain it came from Nevada, but to confirm that we’d need to know exactly what the substance is,” said Mary Wister of the National Weather Service (NWS). “Nevada had incredibly strong winds Thursday night and Friday morning, and the dirt there is a very alkaline dust.” Wister noted that low-elevation wind gusts that have been blowing north likely carried the dust to rain clouds that could have then deposited the milky rain across the region in question.

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The other theory by the weather scientists postulates that higher-altitude winds may have carried ash from Japan’s erupting Sakurajima volcano across the Pacific Ocean and deposited it in the Pacific Northwest via rain. But Wister said this theory is less likely than the Nevada scenario, and added that without chemical analysis of the rain’s residue it would be impossible to determine the exact origins of the rain.

She notes that the NWS doesn’t have the equipment needed to perform that kind of testing, so none has yet been done. “We’re hoping somebody else does tests and shares what they find,” Wister said.

Via Reuters

Images via NWS Spokane