There had been a four-year drought in Iran, which came to a spectacular end in February 1972 not with long-awaited rainfall, but. in the form of an intense blizzard that lasted for a week and blanketed the country.

Virtually all Iran’s 1,636,000 sq km (631,000 sq mi) landmass vanished beneath a covering of snow that was so deep in places it literally buried thousands of people, many of whom sat tight in houses that turned into freezing death-traps long before a slow thaw revealed the true horror of this extraordinary happening.

Tire tragic outcome is perhaps not surprising, for this was the worst blizzard ever recorded in world history. The snow was at least 3 m (10 ft) deep, though some places – mainly in southern Iran – saw coverage as deep as 8 m (26 ft). Furthermore, the extent of the blizzard was a surprise.

Although a mountainous country, Iran’s climate ranges from arid desert to subtropical and temperatures on the Caspian coastal plain in the north rarely fall below freezing.

Inhabitants of the Zagros Mountains in the west were used to hard winters and heavy snowfall, but southerners living alongside the Gulf of Oman and Persian Gulf expected mild winters and hot summers.

Ironically, many of the casualties were recorded in and around the city of Ardakan in central Iran, the second city of Yazd Province, in a region containing several deserts and noted for being one of the most arid parts of the country.

There were no survivors in Kakkan or Kumar and around 100 villagers were buried at Sheklab, by the Turkish border. At least 4,000 people died in this terrible blizzard, many because they simply weren’t expecting or properly prepared to deal with such a totally unprecedented event.

When: February 3-9 1972

Where: Iran

Death toll: Estimated at between 4,000 and 5,000

You should know: The USA’s National Oceanic and Atmospheric Administration (NOAA) puts the Iran blizzard on its list of top global weather, water and climate events of the 20th century, along with the great Iran flood of 1954 that took 10,000 lives.