The familiar British winter has returned, with the first depression of the year lashing the country with torrential rains and howling winds.

A deep depression from the Atlantic was driven on by a strong jet stream high-level wind, battering the western Scottish Highlands yesterday with winds gusting to more than 160km/h (100mph). A band of heavy prolonged rain worked its way down from western Scotland into northwest and southwest England and Wales, and is threatening to set off floods as the prolonged rainfalls run off ground hardened by weeks of deep frost.

This morning the whole county will be full of dark grey skies, although the rains will have weakened by the time they reach the South East. The one enormous benefit, though, is that temperatures will soar into double-digit Celsius as milder air sweeps off the warm North Atlantic Drift current, better known as the Gulf Stream, which delivers the heat equivalent to about a million power stations to the United Kingdom.

The sudden change in weather has come as the reinvigorated Atlantic finally pushed off the stubborn high-pressure system that brought the coldest first half of winter for about 30 years. This was a textbook case of a “blocking” weather pattern, as the anti-cyclone blocked out the Atlantic winds and left the atmosphere stuck in a rut over Britain and much of Europe, creating some three weeks of bitter cold and almost bone-dry conditions. In fact, last night was the first time since Christmas when the UK was free of frost, although the wind and rain made it feel very unpleasant.

How long the new, milder weather pattern will stay is uncertain. High pressure remains lurking over Europe and will battle it out with new depressions lined up in the Atlantic. But the jet stream this week is expected to accelerate to some 320km/h (200mph) as it moves across the North Atlantic from Canada, and so the weather for the next few days will probably remain unsettled and blow hot and cold.

Frogs that have adapted to milder winters have been devastated by the coldest weather for 20 years, which has left a generation of tadpoles frozen solid in ice. At Lizard, Cornwall, the common frog, Rana temporaria, has taken advantage of living in one of the mildest parts of Britain by breeding up to five months earlier than in other regions. So much spawn was produced last autumn that a bumper year for frogs had been predicted for Lizard until the tadpoles were wiped out by freezing conditions as temperatures plunged as low as -7.8C. Frogs in Cornwall tend to breed early. This year their tadpoles were frozen solid

Lewis Smith