In January 1996, 100 million tons of snow fell on the streets of New
York City and nearby Philadelphia was buried under a record 78
centimetres (30.7 inches). Ice storms and sub-zero temperatures
stretched as far south as sunny Florida, trapping people in their homes,
often without electricity. In 1891, easterly winds dumped 3.6 metres
(11 feet) of snow in London. Trains were completely buried under
tremendous drifts and 65 ships sank under the heavy ice and snow.
Blizzards form exactly like thunderstorms. A cold front pushes warmer,
moist air into the atmosphere, condensing into clouds. If temperatures
stay below freezing, snow falls instead of rain. If huge amounts of snow
are accompanied by gale-force winds, it’s possible to achieve a
complete whiteout, when earth and sky merge in a disorienting canvas of
white.
For a winter storm to qualify as a blizzard, there must be sustained winds of at least 58kph (35mph) and less than 0.4 km (0.25 mile) visibility for three hours or more.
