Hail!

Think ‘ice’ and, weatherwise at least, we naturally think ‘winter’.

For water to freeze, the air temperature has to be at or below zero Celsius and for most parts of the world that simply doesn’t happen in summer.

Yet, bizarrely perhaps, icy weather can cause more destruction in summer than at any other time of the year. How so?

The answer comes in the form of hail.

IMG_0605Bouncing off the barbecue and sending us scurrying from our al fresco fun, hail can commonly be seen during summer thunderstorms. High up in the atmosphere, the huge cumulonimbus clouds that produce these downpours are actually full of frozen rain. These spheres of ice can be held in the cloud for hours, melting a little as they fall through the cloud, then re-freezing as vertical air currents scoop them up and send them skywards again – each loop adding a new layer of ice. Eventually the ice becomes so heavy that gravity wins out, the hailstone escapes from the cloud and descends to earth.

So hail can fall at any time of year because the ice simply hasn’t had time to melt – landing on your lawn despite an air temperature well above freezing.

After a heavy storm, the landscape can temporarily be transformed into a ‘winter wonderland’. But those icy drifts are most definitely not made from snow.

IMG_0603In fact some of the most dramatic hailstorms appear during the hottest weather. Why? Because it’s the heat which generates the updraughts that help to grow the hailstones in the biggest of those thunderclouds. In the UK, hailstones the size of golf-balls have been known – shattering windows and denting car rooftops.

But in the tropics, hailstones the size of melons have been reported – and unsurprisingly these can cause fatal harm.

Thankfully, most of the time, hail provides no more than a novel and perhaps surprising interruption. Within a few seconds it’s melted away from our memories, allowing our usual outdoor activities to resume.