Heavy snow has choked parts of New York state, stranding motorists in their cars, forcing people to remain indoors and leaving at least seven people dead.

The snow has been very localised: Buffalo Airport reported just 9cm of snow, whereas the suburb of Lancaster, just five kilometres away, reported a staggering 1.52 metres.

The snow that fell was what is known as "lake effect" snow. This is snow that is generated when a very cold blast of air moves over a relatively warm body of water.

The air can pick up vast amounts of moisture from the water, which is converted to snow and dumped downwind. It is therefore very dependent on the wind direction.

Lake effect snow is very common around the Great Lakes, because at this time of year, the lakes are relatively warm and provide a good source of moisture.

Residents of the towns surrounding the Lakes are well aware of the hazards of lake effect snow, but even in this region, the severity of the weather has caught people by surprise.

Temperatures in all 50 US states dipped to freezing or below on Tuesday, leading to weather which was more reminiscent of January rather than November.

Tuesday morning was the coldest overall across the country in November since 1976.

The extreme weather has now been blamed for the deaths of at least six people in New York, New Hampshire and Michigan.

Those living in snow-covered Buffalo remain glued to the forecast to see the exact direction of the wind, as more lake effect snow is expected on Thursday.

The big thaw is expected on Saturday, and as temperatures rise, the concern will turn to flooding as the snow quickly melts.

Source: Al Jazeera