Winter is about to make a shocking reappearance. It had seemed like spring was in control, with blossom bursting out, trees breaking open leaves and animals waking up from hibernation.

In fact, last Monday was the warmest day of the year so far, almost 19C (66F), a respectable temperature for May let alone mid-March. So it will come as a big shock this weekend when temperatures dive and heavy snows fall.

A northerly blast of air direct from the Arctic is squeezing out the high-pressure system that gave us the warm weather. The forecast maps show isobars pointing almost straight at the North Pole, something not seen since last November.

That means northerly winds will race down with virtually nothing to shelter us from the full onslaught of freezing air. Scotland and Northern Ireland will bear the brunt at first, with the Met Office warning of snowfalls up to 15cm (6in) on uplands. There may also be thundersnow, an unusual combination of thunderstorm and snowfall, hailstorms and tornados.

The cold snap may last only a few days before warm weather returns, but it will feel especially disturbing because we have grown so used to warm, early springs. In fact, snow sometime in March used to be normal. In March 1952, blizzards tore across southern Britain: winds reached 110km/h (70mph) and snowdrifts piled up to 2.5m (8ft) high in the Chilterns.

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