An unusually active spring blizzard has hit the US states of Kansas and Oklahoma, stranding vehicles, downing trees and power lines and building snow drifts more than two metres deep.

The travel-stopping, destructive snow storm is one of the strongest to blanket the region so late in the spring.

On Saturday, the temperature difference between Dallas (at 33C), and Amarillo (at 4C), was 29 degrees Celsius, this despite them both being in Texas, though 600km apart.

Even adjusting for the fact that Amarillo is 800m higher, and so should be cooler, this is still a temperature difference of more than 20C.

Tornadoes are spawned where two contrasting air masses collide and push up thunderstorms. Generally speaking, the bigger the contrast, the bigger the storm and the bigger the tornado.

The resultant deadly tornadoes on Saturday ripped through Texas, Arkansas, Mississippi and Missouri. These were accompanied by enough rain to cause flash floods and for rivers to burst their banks.

While the tornadoes and flooding may be expected in spring, the amount of snowfall was unusual. Snow in the cold air reached Amarillo before dawn on Saturday following a drop in temperature of 19C in 15 hours. Approximately 8cm of snow then fell.

The Kansas Highway Patrol shut down numerous roads and urged people to stay at home. The city of Colby ended up with 50cm of snow by the time that the blizzard had finished.

Oklahoma was facing similar conditions with snow in Boise City, in the Oklahoma panhandle, eventually reaching a depth of about 30cm.

These figures in northern Texas and the Oklahoma, represent the deepest snowfall at this time of the year for nearly 40 years. For Kansas, if the figures are confirmed, it will be a new record.