29 Mar 2012

From summer-like warmth to a winter-like chill

The weather across the UK has been remarkable during the last week, with warmth reminiscent of summer for most places, lulling us into a false sense of security that the sunshine is here to stay.

Temperatures have widely reached the low 20s, with Scotland setting a new maximum temperature record of 23.6C for March – recorded at Aboyne in Aberdeenshire on Tuesday afternoon.

The old record of 22.2C was set in 1957 at Gordon Castle, Moray and again in 1965 at Strachan, Kincardineshire.

The record was actually broken incrementally three days in a row – at first on Sunday with 22.8C at Fyvie Castle, then on Monday at Cromdale with 23.2C, before finally reaching 23.6C at Aboyne on Tuesday afternoon.

This spell of summer-like warmth has been due to an area of high pressure that has been sitting across the UK for the past week, bringing cloudless skies, light winds and unbroken sunshine.

Whilst the days have been warm, the nights have been quite chilly with some mist and fog, as well as a touch of frost in places.

Such a huge daily range of temperatures has been down to two main reasons – night and day are still roughly of equal length and the air has been very dry.

When the air is very dry, the temperature is able to rise and fall more quickly because it doesn’t have use any energy to condense or evaporate moisture in the air. All of the energy goes into heating the earth’s surface and the air just above, lifting the temperature.

With night and day still roughly of equal length, there is enough time at night for heat to escape up into the atmosphere, allowing the temperature to fall quite markedly from the daytime warmth.

The next few days, however, will see a big change in how the weather feels. As the area of high pressure that’s been sitting across us for the past week drifts to the west, colder air will sink southwards.

This means there’ll be a notable drop in temperature, with highs of just 10-14C this weekend, with more cloud, a cool breeze and some light rain possible for north western areas.

Early next week, there are signs of it turning colder still, with a plunge of arctic maritime air moving across the UK.

Tuesday and Wednesday will see temperatures reaching just 5-10C by day and dropping below freezing at night with a widespread frost – something to note if you’re a keen gardener.

There’ll also be a mixture of sunshine and showers, with some of the showers possibly turning wintry across northern areas, mainly over the hills and mountains.

So after a taste of summer-like warmth, we may well be digging out the winter clothing one last time, a reality check that it as after all still only late March.

Don’t forget you can get the latest five day forecast on the Channel 4 Weather website and you can always ask me your weather questions on Twitter – @liamdutton

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