The 2007 Siberian orange snow was an anomalous phenomenon that happened on February 2, 2007 when an orange-tinted snow fell across an area of 580 square miles in the Siberian Federal District in Russia, as well as into the neighbouring oblasts of Tomsk and Tyumen. It was most likely caused by a heavy sandstorm in neighbouring Kazakhstan.
This orange snow was malodorous, oily to the touch, and reported to contain four times the normal level of iron. Though mostly orange, some of the snow was red or yellow. It affected an area with about 27,000 residents. It was originally speculated that it was caused by industrial pollution, a rocket launch or even a nuclear accident. It was later determined that the snow was non-toxic. However, people in the region were advised not to use the snow or allow animals to feed upon it. Coloured snow is uncommon in Russia but not unheard of, as there have been many cases of black, blue, green and red snowfall.
The phenomenon was most likely caused by a heavy sandstorm in neighbouring Kazakhstan. Tests on the snow revealed numerous sand and clay dust particles, which were blown into Russia in the upper stratosphere. The speculation that the colouration was caused by a rocket launch from Baikonur in Kazakhstan was later dismissed, as the last launch before the event took place on January 18th.
Russia’s environmental watchdog originally claimed that the coloured snowfall was caused by industrial pollution. It stated that the snow contained four times the normal quantities of acids, nitrates, and iron. However, it would be nearly impossible to pinpoint a culprit if pollution were the cause, as there are various industries nearby, such as the city of Omsk, which is a centre of the oil industry in Russia.