A regular summer's day in the UAE turned to heavy rain and strong winds as an unexpected storm swept over Dubai on Friday. Gusts of wind picked up just before 4pm under an overcast sky with swirling sands reducing visibility to a few meters. Heavy rain and a downpour of pebble-sized hailstones followed soon after in the Silicon Oasis area of emirate. Motorbikes were knocked off their stands and trees swayed as the sandstorm flung empty cartons and boxes stacked outside shops into the air. Pedestrians ran for shelter as main roads flooded. The country's forecaster, the National Centre of Meteorology, shared videos of the downpour in Al Aweer, just beyond International City, on Twitter. Similar conditions were reported in Al Madam in Sharjah. The bureau reported heavy rain over Academic City in Dubai and upgraded its warning system from yellow, "Be Aware", to orange, "Be Prepared", in the north eastern part of the country. The warning calls on residents to be on the alert as hazardous weather events are forecast. It advises the public to comply with any advice issued by authorities. The bureau said fresh winds would pick up blowing dust and reduce visibility to less than 2km and warning motorists to drive extra carefully as a result. The Storm Centre showed videos of hail falling in Al Dhaid and Mleiha in Sharjah as well as eastern areas of Dubai. Among those who were caught in the rain was none other than Sheikh Hamdan bin Mohammed, Crown Prince of Dubai, who posted videos of himself while in the car as the storm battered down. It may seem like an unlikely pairing, but hail can be common to countries that fall between the Tropic of Cancer and the Tropic of Capricorn during the summer. This is because surface temperatures are warm enough to promote the instability associated with strong thunderstorms but the upper atmosphere is still cold enough to support ice. Hail forms when strong currents of rising air, known as updrafts, carry water droplets high enough that they freeze. A particularly strong updraft can allow the hailstones to grow large enough that they do not melt by the time they fall back and reach the ground. Once they grow large enough to begin falling, the can drop as fast as 140kph, causing some damage when they land.