The photos are surreal, like a Martian ski slope or a toasted marshmallow sky.

But why did some people in Eastern Europe last week see the world in sepia tones? The answer lies hundreds of miles away.

The orange-brown filter applied briefly to that part of the world was caused by dense Saharan dust kicked into the air and swept north, experts said.

The process began when a polar jet stream made its way farther south than usual last week, bringing the strong winds and thunderstorms needed to whip up the dust, according to Tyler Roys, a meteorologist with AccuWeather.

“A trail of storms have been going through Italy, the Balkans, Ukraine and into western Russia, and finally this last storm that finally moved through, an area of lower pressure closer to the northern coast of Libya, helped pull the dust up,” he said in a phone interview.