Households have been urged to pack ‘grab bags’ of valuables and essentials, as three million homes face the risk of flooding in the coming days.
The summer’s second prolonged heat wave came to an abrupt end on Monday when thunderstorms barricaded some areas with almost three centimeters of rain.
Forecasters have warned of an “unbelievable deluge” this week after the driest July on record and driest first half of the year for decades caused drought across parts of Britain, leaving the country parched.
The Met Office has issued a yellow thunderstorm warning for most of the country on Monday and Tuesday as the conditions could cause flooding, transport disruption and power cuts.
It will remain in place for southern England on Wednesday, where communities could be cut off by flooded roads and the chance of fast-flowing or deep floodwaters could cause life-threatening conditions.
More than three million households in England are vulnerable to surface water flooding, the Environment Agency estimates, with 300,000 more at risk in Wales and Scotland.
People living in “low-lying properties” should ensure their valuables are “ready for use”, or “on a higher level of your house”, due to the current high flood risk.
Met Office meteorologist Clare Nasir told Sky News: “For low-lying properties, which may have been built on a flood plain, yes, there is a risk of property flooding.
“Get all your documents, whether it’s your cell phone, your passport, etc., all the things you don’t want to be damaged by flood water, and make sure they’re ready for use or on a higher level of your house.”
She added that the downpours overnight and into this morning are “the wrong kind of rain that we need for the ground”, as the ground is too hard to absorb it.
The meteorologist continued: “What we’re looking for is some kind of continuous rain, moderate rain, rather than this incredibly intense burst, which is currently moving up over more southern parts of England.
“So we’re not out of the woods yet.”
Heavy showers caused flooding in areas of Cornwall and Devon on Monday afternoon, while thunderstorms developed in east coast counties such as Essex, Suffolk and Lincolnshire.
Met Office meteorologist Tom Morgan said most places stayed dry on the day, but added: “There have been areas of the country that have seen the heavy showers today mainly in the south west of England.
“We have seen some flooding in parts of Cornwall and Devon,” he said, adding there had been “very difficult driving conditions, flooding, some hail with thunder and some lightning.”
He said the flooding also “creates the potential for some power outages and some potential flooding, particularly in cities and more urban areas”.
“There are also thunderstorms in east coast areas of Suffolk, Essex and Lincolnshire,” he said, but added that these are not expected to have a significant push bar causing any difficult driving conditions.
Mr Morgan continued: “There is just as much potential [Tuesday] to be as effective as it has been today.’
Flood warnings had also been issued for parts of west London near the River Thames, including Richmond, Chiswick and Putney, but they have since been lifted.
Speaking on Monday, Mayor of London Sadiq Khan said: “We learned a lot from last year in July when there was flooding caused by a huge amount of rain – two months’ rain – in just a couple of hours and people’s homes, businesses and public transport were flooded.
“Speaking to the Met Office, the Environment Agency and many others, we are concerned that over the next few days we could see a huge amount of rain in a short space of time which could lead to flooding.
“I have written to tens of thousands of Londoners who live in homes that could be affected by flooding.
“My message to Londoners is to get in touch with Floodline, go to your local authority’s website to see what you can do to reduce your chances of being flooded but also to minimize the consequences for you,” he said, advising people also checking that they are insured and what these details are, as well as preparing a grab bag.
Mr Khan said: ‘[We are] are working closely with the water companies, the fire service, Transport for London, local councils and other partners to make sure we are as ready as we can be, but the bad news is that there could be flooding if there is heavy rain in a short period of time period of time.’
Earlier, Professor Hannah Cloke, an expert in hydrology at the University of Reading, explained why there is potential for flooding in drought-stricken areas.
She said: ‘The butt is very dry and when it’s that dry it feels a bit like concrete and that water can’t get in so it just drains off.
“There’s the damage to homes and businesses these floods can cause, and the inconvenience of transport disruption, but if it’s very heavy in one place it can also be very dangerous.”
On how it could affect cities and towns, she said: ‘If you get heavy rain in a city, the drainage system can cope with it up to a point, but if it’s really heavy rain it can overwhelm the system – the rain can’t run away fast enough .
In rural areas, Professor Cloke said this type of flooding often hits low points on roads and under bridges, adding: “It’s very dangerous to drive through floodwater.”
Explaining why this heavy rain will not relieve drought-stricken areas, she said: ‘It really is a drop in the ocean. It doesn’t soak into the soil, that’s how we really need it.
“We need it back in the system where it can be stored. We really need a long winter of rain to replenish this.’
Meanwhile, Christine Colvin, director of advocacy and engagement at the Rivers Trust, said there is a risk that people will not take the drought seriously in the coming days “just because it’s raining”.
“We want people to keep this rainfall event in context and as part of the bigger picture, and the bigger picture is that we’ve actually still had an incredibly dry year as well as a dry summer, and it’s going to take sustained rainfall to replenish our supplies, she said.
“Just because it’s raining doesn’t mean the drought is over.
“It seems very counterintuitive, but it’s going to take sustained rain to replenish the supplies we actually use, which are the aquifers and the managed storage in our reservoirs.”
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