Met Office says some areas could see 2-3cm of rain in an hour – almost half of the UK monthly average for all of June

This article is more than 6 years old

This article is more than 6 years old

Severe weather warnings have been issued for Saturday, with some areas of Britain expected to see nearly half an entire month's rainfall in just an hour.

The Environment Agency has issued "low risk" flood alerts for most of the UK.

The Met Office said thundery rain was expected to begin early in the morning, with showers likely until the evening.

Some areas could see 2cm to 3cm of rain in an hour – almost half of the UK monthly average for the whole of June of 7.3cm. The cause is warm, humid air moving in from Europe which creates a risk of downpours when it mixes with cooler air over the UK.

Met Office spokesman Dan Williams said the downpours would be "pretty heavy". He said: "We are looking at the potential for some localised flooding because the downpours are potentially heavy enough that we could see so much rain fall in a short space of time that it can't drain away fast enough."

Regions where yellow "be aware" warnings for rain are currently in place are north-west England; north-east England; Yorkshire and Humber; West Midlands; East Midlands; east of England; south-west England; London and south-east England; Strathclyde; Central, Tayside and Fife; south-west Scotland; Lothian borders; Northern Ireland; and Wales.

The Environment Agency said: "Heavy rain with isolated torrential downpours may bring some river and surface water flooding on Saturday across all of England, except for Devon and Cornwall, and all of Wales, except for Pembrokeshire."

Dr Roger Brugge, a meteorologist at Reading University, said a total of 18in (462mm) fell between January and May – around 1in (25mm) more than in any other first five months of a year since records began in 1908.

His colleague, Dr Hannah Cloke, a flooding expert, said: "We could see flash floods in some parts of Britain if rainfall this weekend is as intense as has been predicted.

"The problem is likely to be exacerbated in areas where the ground is still wet from the winter floods, particularly in catchments with high groundwater levels and where rivers are still high following Britain's wettest winter ever."

Some areas however are expected to enjoy warm temperatures and some bright spells in between the showers.

The Met Office said the mercury could rise as high as 25C (77F) on Saturday and Sunday in London and the south-east – not far short of the warmest temperature of the year so far, 26.3C (79.3F).

Williams said: "It is going to be one of those warm but humid days where you could see some bright spells but also some heavy showers as well."

He said the downpours would ease by Sunday when there would be some "good, dry and bright spells", particularly in southern and eastern parts of the country and only a risk of light rain in some areas.

Next week is likely to be "slightly unsettled" with some dry and bright conditions along with light showers, he added.