I survive winters by abiding by these three simple rules: enjoy the white snow, drive carefully in the grey snow and don’t eat the yellow snow. I don’t know what to do if orange snow falls and neither did the residents of the Russian city of Saratov when it was blanketed this week with a deep covering of orange flakes.

Saratov is a major port (population over 800,000) on the Volga River, 858 km (533 miles) from Moscow, and has a moderate (for Russia) climate with an annual snowfall of about 163 centimeters (64 inches) which, until now, has never been orange.

The orange snow was widespread and of various shades of orange along with patches of yellow and brown. Saratov’s residents were rightly skeptical to avoid eating snowflakes or jumping in the juice-colored banks until finding out what caused it. The most likely reason, according to Saratov weather forecast service director Mikhail Boltukhin, was a cyclone that blew colored sand from Africa’s Sahara desert into Siberian snow clouds.

The air coming from the West contains tiny particles of sand, which give the falling snow an orange hue. Similar phenomena have been observed recently in various districts of the region and in other parts of the country, particularly in Crimea.

Well, the second part is true. In 2007, an orange snow covered over 1500 sq km (570 sq miles) in the Omsk region of Russia. That stuff was oily and smelled rotten and was blamed on the area’s oil industry, although it also contained four times the normal level of iron ore.

Colored snow can have other causes. Red-and-pink watermelon snow is common in alpine regions and gets its colors and telltale smell of watermelon from an algae (Chlamydomonas nivalis). So-called blood snow falls near Blood Falls in Antarctica’s Taylor Glacier for a different reason. Iron-rich saltwater leaking from an ancient reservoir under the glacier oxidizes when it hits the air and turns the waterfall and snow blood red.

Saharan sand, algae, oxidation … or something else. What do you think was the real cause of Saratov’s orange snow?