The Anglia region has seen as much as a fortnight's worth of rain in just 12 hours.
Holbeach in south Lincolnshire had 25 mm (1 inch) of rain up to 10am on Friday morning. Usually the whole month of July has 45 mm in an average year.
The Environment Agency has issued more than 40 flood alerts for the Anglia region as torrential rain hit the area.
Despite the rain, crowds had not been deterred from heading to the Olympic Torch events in Suffolk and Essex.
Fans heading to the British Grand Prix at Silverstone are being urged to be patient as organisers battle to get racegoers parked up near the circuit.
A spokesman at Silverstone said: '"The weather conditions are far from ideal but we have contingency plans in place and are trying to deal with the situation as quickly as we can.
"There will be delays at car parks and at camp sites, but we want to get people parked up safely, and we're asking everyone to be patient, allow more time for their journeys, so we can make it a great weekend."
More than 100,000 F1 fans are expected at Silverstone in Northamptonshire over the weekend.
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One event to fall victim to the weather is the Summer Extravaganza at World Horse Welfare’s Hall Farm in Snetterton, Norfolk. It had been due to take place on Sunday 8 July but has been cancelled.
Rainfall totals in the Anglia region in the 12 hours to 10am on Friday 6 July
- Holbeach, Lincs - 25 mm
- Norwich - 18 mm
- Andrewsfield Essex - 15 mm
- Marham, Norfolk - 12 mm
- Sawtry, Cambs - 11 mm
- Santon Downham, Suffolk - 10 mm
- Bedford - 9 mm
- Northampton - 9 mm
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