Britain is facing a flooding timebomb this autumn and winter, with huge amounts of underground water stored up by incessant summer rain ready to burst out as floods the next time heavy rains return.

The Environment Agency is giving warning of “an enhanced flood risk” for England and Wales, although where and when any flooding strikes will depend on the weather patterns. Forecasters are predicting a wet autumn across much of Britain.

If the soil dries out this autumn the danger could subside, but time is already running out — evaporation slows down as sunshine becomes weaker and trees and plants take less water from the ground. If the seasonal forecasts are correct then continued rainfall will increase fears of further flooding, especially if the rains come in heavy bursts, as happened in June and July.

There is a fine balance between healthy water supplies and disastrous flooding. Aquifers in Britain hold at least 20 times more water than the reservoirs and provide about a third of the drinking water supplies, with a far higher proportion in South East England.

The aquifers were recharged fully during the summer, safeguarding water supplies well into next year. But the saturated ground also means that parts of the country could be on flood alert throughout autumn and winter, with no chance for the ground to dry out until the spring.

The seeds of this problem began in May with the first bouts of heavy rain. Since then the weather has been exceptional. Rainfall for May-July was the wettest on record, dating back to 1767, across England and Wales. Soils are at their wettest on record for the summer, many rivers broke records for water flow in July, many reservoirs are filled to capacity and springs that have been dry fo

Experts were amazed by the extent of flooding — drier soil usually leads to fewer floods than in winter, and those that occur tend to be localised, often after a torrential thunderstorm. This summer’s floods, caused by heavy and broad bands of rain, were widespread.

“This summer was unprecedented,” Terry Marsh, of the Centre for Ecology and Hydrology at Wallingford, in Oxfordshire, said. “The wetness of the soils and the river flows in the lowlands of England are more typical of winter than summer. I’ve never seen anything like that before.”

These are exceptional weather patterns — the last time that so much rain fell in the summer half of the year was in 1912, and before that in 1879. Usually the ground dries out during the summer as trees and plants soak up huge amounts of water, and by August lawns are often turning yellow and the ground is parched, reducing the likelihood of flooding. Deep underground, water levels drop gradually in porous subterranean rocks known as aquifers.

During autumn and winter the ground begins to soak up rainfall, sometimes leading to flooding. The rainwater also percolates deep underground and recharges the aquifers.

This summer the rains have been so heavy that the ground has been supersaturated, rivers have burst their banks and aquifers have been recharged.

“The really strange thing is that the recharge happened in summer, when there is usually no recharge after April. All boreholes are at peak levels, which is incredibly unusual,” Professor Alan Jenkins, water science director at the Centre for Ecology and Hydrology, said. “As we run into autumn, river catchments are in a much more sensitive state, and there is the possibility that more catchments will be susceptible to flooding.”

The Environment Agency said that people should be prepared for the prospect of more disruption. “We urge people to be aware of the flood risk this autumn and winter and be prepared,” Simon Hughes, flood risk manager, said.

The agency is taking out national adverts and holding flood surgeries in flooded areas to get their message across. After a fraught summer, this could be a nerve-racking autumn and winter.

Torrential rain has caused flash flooding in parts of Devon. Fire crews pumped several feet of water from the basements of businesses and homes in the Torbay area.

Torquay, Paignton, Brixham, Dawlish and Kingswear were affected by the severe weather on Monday morning. Businesses in Torquay were forced to close after about 30cm (1ft) of water rushed down Fleet Street and through shop doorways. Denise Shears, from Waycotts estate agents, said that drains were unable to cope with the volume of rain and that sandbags put out to prevent flooding were washed away.

Torquay and Paignton suffered the worst of a torrential downpour, with dozens of properties and businesses badly affected. Police said that a leat burst its banks in Paignton, sending a flow of muddy water across Dartmouth Road.

Manhole covers were reported to be moving out of position across the region.Boundary Road in Brixham was closed off after traffic was unable to negotiate the depth of water on the carriageway.