The small town of Ottery St Mary in East Devon was hit by extraordinary weather this time last year. In the early hours of the morning a terrific downpour of rain and hail crashed down in cascades. The River Otter burst it banks and set off a flash flood that turned roads into torrents, ripped up hedges and tore up road surfaces. The rains also swept up masses of hail and dumped them in vast heaps up to 1.2m (4ft) deep in the town, which gave the impression of ice floes floating along the streets and crushing cars in ice. “It was like walking into the Antarctic. The water was freezing,” described one witness. The town was cut off completely, homes were deluged and more than 100 people had to be evacuated, some by helicopter. The damage to homes, roads and cars was estimated to have cost £1 million.

According to a recent report in the Royal Meteorological Society’s journal Weather, more than 200mm (7.9in) rain and up to 30cm (12in) hail may have fallen in only two hours. In fact, the weather that week was very strange, with an early snowfall across much of southern England two days beforehand. When a mass of mild, moist air swept in off the Atlantic it hit the very cold air above and detonated into a localised storm over Ottery St Mary. Once in situ, the storm was pumped up by another flow of mild, moist air sweeping off the Channel, which in late autumn is much warmer than the adjoining land. As the sea air was funnelled up the Otter Valley it blew up the storm into a self-feeding monster.