A record-breaking snowfall event unfolded in far eastern Russia last week when the town of Petropavlovsk-Kamchatsky, located on the Kamchatka peninsula's east coast, received more than 1.8 metres (6 feet) of lying snow in places. Strong winds accompanying the snowfall caused extreme drifting of more than 3 metres against buildings and cars. Two key ingredients combined to cause such an extreme snowfall event. Strong Pacific low pressures dragged moist air from the tropics northwards, which clashed with cold Arctic air already over the region. Conveyor belts of tropical air are called atmospheric rivers and often bring heavy rainfall to places such as California.