After last Thursday’s storm, the worst for 17 years, the UK is now going to suffer another shock — winter is about to make an appearance. Although the country has been battered by wind and rain this winter, temperatures have been extraordinarily high.

This month has been running about 4C (7.2F) above normal, bringing out spring flowers and butterflies, and thoroughly confusing wildlife. But temperatures are set to nosedive this week as a large block of high pressure drifts in from the Atlantic, sweeping down ferociously cold polar air, some from deep inside the Arctic Circle.

This anticyclone began life in the US, where it brought a savage icestorm and snow that killed dozens of people and caused widespread chaos. That high-pressure system then slid off into the Atlantic, and as it approaches Britain will sweep the cold northerly air down, hitting East Anglia and Kent particularly hard. These areas can expect hail, sleet and snow tomorrow and on Wednesday. The North Downs in Kent may have some of the heaviest snow. Even London, more used to basking in spring-like temperatures, will probably see a dusting of snow at least.

And for much of Britain, sub-zero temperatures, diving to minus 4C (24F) or -5C at night, will bring another reminder that this is midwinter: some severe frosts will appear. Although high pressure usually brings calm conditions, low pressure over Europe will leave Britain fairly windy, making rescue plans for the stricken ship off Devon problematic, with offshore northerly winds a strong possibility. The wind will be created by a sandwich of air pressure — high pressure to the west of the UK and low pressure to the east, over Europe. But the anticyclone will bring some welcome sunshine and blue skies after the gloom and grey skies of recent weeks, and it will be much drier as well, giving relief to areas under threat of flooding.

However, as the high pressure drifts farther over Britain, we can expect calmer and slightly milder weather by next weekend, about 6C or 7C. Conditions will remain drier.

But is this remarkable? In a normal winter none of this would raise an eyebrow, but, after such a long run of mild weather, the cold will be a shock to the system. And there are signs of something altogether much more sinister in February — a build-up of high pressure over Scandinavia that could plunge the UK into a Siberian freeze.

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