In early February, residents in eastern Washington were scratching their heads about a strange rain that fell from the sky.
A milky-colored rain fell Feb. 6 as part of a recent onslaught of storms to hit the Northwest United States.
The National Weather Service office at Spokane, Washington, investigated the phenomena and determined it was probably dust carried by a Feb. 5 storm from south-central Oregon near Summer Lake, the office reported on its blog.
"A trajectory forecast model agrees that dust from this location would have traveled over the Pendleton, Tri-Cities and Spokane areas on the morning of the 6th," the office said.
It matched the area from where the NWS received reports of the rain.
It's not unusual for dust to color the rain in the Northwest but the timing makes it unusual, AccuWeather.com Senior Meteorologist Jason Nicholls said.
"This phenomena is more typical in the Northwest toward the end of long, hot and dry summer where local dust mixes with the first rains after the long, dry and hot summer," Nicholls said.
Besides milky rain, there have been many incidents of strangely-colored precipitation in different areas of the world.
Watermelon snow is just like it sounds: It has a watermelon color.
Watermelon snow can occur anywhere under the right conditions, Nicholls said.
"There have been reports of watermelon snow in the Scottish Highlands, Greenland, and Aristotle even wrote about it. The phenomena is most common in early spring," he said.
It's the result of algae blooms that produce a red color, Nicholls said.
Volcanic ash can also produce a milky color in rain, Nicholls said.
There was some speculation that the Sakurajima volcano in Japan could be responsible for the Washington rain.
However, the Nevada dust storm was the most plausible reason, the NWS said.
Dust from the deserts can change the color of rain, even turning it into a "blood rain" with a reddish look.
It is most common in the western Mediterranean where the main sources of desert dust reaching the Iberian Peninsula and the Balearic Islands is from the Western Sahara, Atlas Mountains in Morocco and Central Algeria, Nicholls said.
More than 500 instances of blood rain have occurred since 1900, according to a University of Arizona database.