Residents living in southern England should be prepared for more Boscastle style flash floodings by the end of the century warn the Met Office.
Over the next 85 years the warmer climate will lead to more torrential downpours, causing rivers to burst their banks and homes to flood.
The warning came after the Exeter-based forecasters changed their models from 20km square areas to 1.5km squared and found the impact of climate change had been underestimated.
The number of flash storms will rise to 117 by 2100, the Met Office said in a study published in the journal Nature: Climate Change.
Southern England sees around 24 flash storms each summer, when 28mm or more of rain falls per hour.
Residents should also be on their guard for more "localised exteme events", such as the Boscastle flood in August 2004 when torrential rain fell over an eight hour period and the river rose by two metres in an hour.
Elizabeth Kendon, of the Met Office Hadley Centre in Exeter, said: “The 1.5 km model shows a future intensification of short-duration rain in summer, with significantly more events exceeding the high thresholds indicative of serious flash flooding.
“This implies that previous interpretations of future regional climate change scenarios should be revisited, as changes in rain events could have been underestimated.”
This new forecast is that more events would exceed the Met Office and Environment Agency Flood Forecasting Centre guidance threshold for serious flash flooding.
The upside is that heatwave summers will also be the norm in Britain by the 2040, with half recording average temperatures higher than in record breaking 2003.
Some parts of the country have already had the wettest May for up to 47 years and the people of the Somerset Levels know all about the increased risk of flooding.
In the short term we can expect a “dull, dank and miserable” start to the week, with heavier rain from Wednesday to Friday plus thunderstorms.
Although there’s no sign of the promised heatwave on the horizon, the weathermen say more settled” conditions are expected from mid-month.