Weatherwatch: Sahara dust

The Hill of the Acropolis, Athens, hazed by a huge cloud of Saharan dust that covered the city in the spring of 2008. Photography: Simela Pantzartzi/EPA

It was the height of the happy 60s and papers were full of strange stories, but the events of July 1, 1968 were weirder than usual. A sweltering summer heat wave finally ended as a depression swept the South of Britain, bringing rain and cooler conditions. But the nature of the rain caused people to take a second look: instead of the usual things transparent, he is of red brick. After the rain stopped, came another big surprise: every available surface was covered with a thin layer of sand, varying in colour from red through Orange to yellow.

This was the most extreme example of engraving of a quite regular phenomenon: the fall of "Dust of the Sahara". This occurs when the sandstorms in North Africa pushing sand into the atmosphere, that it is, then northward by wind until fall, usually along with rain, here in Britain, 1500 kilometers to the North. In 1984, there were declines in the Sahara dust until the middle of November, during a warm spell Friday when temperatures reached 19 C. These southern winds brought another surprise: four pale Swifts, the paler version of our own visitor summer family, they were spotted by birdwatchers in scattered places in Wales to Kent. As air feeders, pale Swifts had been caught up in the same airflow as the sand. Before this multiple unusual sighting, there were only two records of this species in North Africa in Great Britain.

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Weatherwatch: Beware of the swarms of biting flies at dusk

Tourists in Loch Broom, Scotland are attacked by flies. Photograph: Murdo Macleod, the Guardian

This August will be dark clouds of creatures bloodsucking in Scotland. Swarms of biting midge Scottish enjoyed a large increase in numbers this summer thanks to its ideal climate, as the rains and the Sun have led to the breeding conditions perfect.

It all started in the bitterly cold winter, when the midge larvae survived underground under a blanket of snow. Birds that feed on them gone less well, though, and in the spring of the flies had many fewer predators to worry about. The warm spring and abundant rain brought the larvae in the Earth flying around as adults. And with much more rain this summer, the conditions are ripe for an explosion in numbers midge, appropriate for the school holidays. The signs are ominous, because earlier this summer midge traps collected two or three times the number of flies that have been in the past two years.

Black swarms of flies descend on unwary tourists dare to venture outside in the evening. Only females flies bite, however, that they pierce the skin and sucking blood. And it is traditionally the Western side of Scotland which is riddled with, because the flies require large amount of rain, more than 120 cm by year, moist air and a peaty soil, acid, which is what the Highlands and the Islands offer abundant.

The best advice is to avoid leaving in the evening, or cover from head to the toe and the use of insect repellent.

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