UK heatwave
Water consumption in London increases by 14% on a sweltering day Ian Walton/Getty

Temperatures in the UK are expected to soar this week, reaching highs of 25C on Wednesday (17 August) in the south-east. The Met Office has issued warnings of an "absolute drought" in England, alongside advice on how to deal with sunburns as UV rays reach high levels during the heatwave.

Between 2 and 13 August, there has been only 5mm of rainfall, which is 14 times lower than the 70mm monthly average for the UK. Thames Water has prepared an additional 450 million litres of water per day for the south of England ahead of temperatures rising by mid-week, adding that water consumption in London increases by 14% on a hot day.

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Mark Jenner, Head of Operations Systems at Thames Water, explainedd: "In some places demand for water in the evening nearly triples, so it's up to us to do the math and put more water through our treatment works and get that extra water into supply."

Meanwhile, the Trades Union Congress(TUC) has also issued warnings to employees working outside during the high temperatures, noting that they are at risk of sunstroke, sunburn and even skin cancer. TUC General Secretary Frances O'Grady urged bosses to follow measures to protect their staff who work outdoors, including allowing them to take frequent breaks and review working times.

The Met Office's UV index relays warnings based on the strength of the sun and notes that UV rays can be high even when there is cloud cover and it is not particularly hot. On 16 and 17 August UV rays across the UK are expected to reach high levels between 1pm and 4pm GMT.

"We treat our farmyard animals better than some of our agriculture workers," said O'Grady. "At least animals get shelter and a supply of water in the heat. Working outdoors in sweltering conditions can be unbearable and dangerous and bosses must ensure their staff are protected."

However, the hot air that was expected from Spain and north Africa has blown away, with the Met Office saying that the air will not be as hot and humid as it could have been. The fine weather is also not expected to last until the weekend, yielding to unsettled conditions and some showers.