Some parts of the Anglia region have seen nearly a month's worth of rain in less than a day as a deluge breaks a three-week drought.
Summer has been brought to an abrupt halt after the soaring temperatures of last week were replaced by torrential downpours.
The Met Office has issued a yellow weather warning for continuing heavy rain which could cause localised flooding.
Santon Downham on the Suffolk-Norfolk border has been the wettest place in the UK with 49.8 mm (2 inches) of rain in the 12 hours from 9am until 9pm on Tuesday 27 June.
Normally, in an average year, Santon Downham would expect 58 mm (2.3 inches) of rain in the entire month of June.
Rainfall totals in the Anglia region in the 12 hours to 9pm on Tuesday
49.8 mm in Santon Downham, Suffolk
27.0 mm in Marham, Norfolk
23.6 mm in Cavendish, Suffolk
21.0 mm in Higham near Bury St Edmunds, Suffolk
20.6 mm in Houghton, Norfolk
17.2 mm in Weybourne, Norfolk
17.0 mm in Cromer, Norfolk
13.2 mm in Tibenham, Norfolk
Despite the sudden switch from summer to conditions more akin to autumn, it looks likely that June 2017 will end up being the hottest June for more than 40 years.
Temperatures had been pushing close to the record-breaking June of 1976 which then heralded the start of a long, hot heatwave of a summer.
The thermometer reached 32°C (90°F) in some parts of Bedfordshire last week. In contrast, the highest temperature in the Anglia region on Tuesday was 19.2°C at Writtle in Essex.