At long last the promised barbecue weather has arrived – although too late for the school holidays. September is turning out to be dry, sunny and fairly warm. And the outlook is for plenty more sunshine to come, marking the first time for well over two months that the entire country has shared fine weather.

Until now the nation has been split by an invisible line running diagonally from the South West to North East — wet towards the North and dry towards the East. Last Tuesday witnessed the most surreal contrast in weather. In the South, a mini-heatwave reached a dizzy 28.7C (83.7F) at Gravesend, Kent, the seventh-hottest day of the year. Even Aberdeen enjoyed 22C (72F). At the same time, though, northwest Scotland was hit by a full-blown gale, with winds gusting to 116km/h (72mph) and more than 60mm (2.4in) of rain in 24 hours, which set off a landslide in Argyll, west of Loch Lomond.

Records have tumbled as the rain crashed down. Southwest Scotland had its wettest August on record, and the weather station at Eskdalemuir observatory, Dumfries and Galloway, had its third-wettest month yet.

The bleak weather carried on into this month and on the Isle of Skye rain fell for more than 50 days, the longest uninterrupted spell of wet weather since 1861. Farmers have struggled to harvest crops in appalling conditions for the third year running. “It’s as bad as last year,” said Adrian Ivory, a farmer in Perthshire. “Ground conditions are hellish.”

But as an old saying goes, “September dries up wells or breaks down bridges”. In southeast England and East Anglia rainfall has been so meagre that rivers are starting to run low. Kent was the driest area in Britain, with 114mm (4.5in) of rain, a quarter below its average, resulting in bumper fruit crops.

In fact, hardly a drop of rain has fallen for weeks over the southeast corner of England, from Suffolk to West Sussex. The seaside resort of Clacton has basked in six weeks of dry conditions, which helped to bring more than 800,000 visitors to the famous pier. “We were very lucky in Clacton, we missed the bad weather, even though we suffered when the forecasts got it wrong and said it would rain when it didn’t,” said Billy Ball, director of Clacton Pier.

The whole of East England enjoyed a surge in visitors. “The weather has helped tourism have one of its strongest ever summer seasons,” said Keith Brown, chief executive at East of England Tourism. “The low rainfall gave us a significant advantage over other parts of the UK.”

On Wednesday the weather over the whole UK performed an amazing somersault. Anyone in western Scotland watching their barometer would have seen a remarkable jump in atmospheric pressure as the Atlantic storm gave way to a strong anticyclone. That has brought fine, dry weather across the entire UK.

How long can this weather pattern last? Indications are promising for more dry conditions over the next few days at least, and although rains may return by the end of next week, the high pressure could well return. As for the rest of autumn, temperatures are expected to be above normal.