A searing 35°C heatwave is set to hit the UK as amber extreme heat warnings are issued, with experts predicting seven days of temperatures above 30°C.The Met Office has put amber warnings in place across most of southern England, covering London, the east, the south-east, and parts of the south-west of England and Wales.It means potential health effects are 'likely to be experienced' by vulnerable people and other heat-related illnesses for the wider population, as well as an increase in water safety incidents.The UK Health Security Agency (UKHSA) has even said that it is likely there will be a rise in deaths among older people or those with health conditions in the south of England.The heatwave is expected to last all weekend and into next week in the south, with forecasts of over 30°C every day from Sunday to next Friday in London.There is a 40 per cent chance that this heatwave will breach the record for the UK's highest ever temperature in June - 35.6°C - set in 1957 and 1976, the Met Office said.Saturday has a potential high of 28°C before temperatures rise again from Sunday.Some areas in the south and south-east of England are forecast to reach 32°C on that day and then push up or above 34°C on Monday. The heat has already struck at the Royal Ascot yesterday, where attendees fanned themselves beneath extravagant hats The Met Office has warned of extreme heat in the south of England on Monday and Tuesday, covering London, the east, south-east and parts of the south-west and Wales. Health impacts and even deaths are expected during this heatwaveThey are again likely to reach the mid-30s on Tuesday.Some locations may see temperatures remain above 20°C overnight on Monday and Tuesday, particularly in urban areas.The UKHSA has also issued amber health alerts across southern England, from east to west.This means they expect a rise in deaths, particularly among those aged 65 and over or with health conditions, but there could also be impacts on younger age groups.There is also likely to be an increase in demand for all health and social care services as well as an increased demand for power which exceeds capacity.Travel delays are also likely and temperatures indoors will exceed those clinically recommended.The agency also warned of an increase of drowning cases and cold water shock as more people visit the coast, lakes and rivers to escape the heat. During the last heatwave in May, around 15 people died in tragic incidents like these.The UKHSA alerts have been in force since Thursday at 12pm and will end on Tuesday at 8pm. Less serious yellow heat health alerts are also currently in place over most of the Midlands.Greg Wolverson, deputy chief forecaster at the Met Office, said: 'While heatwave criteria will be met for some in the south and south-east of England over the weekend, with temperatures into the low 30s possible, the warmth will expand and intensify at the start of next week, which, coupled with high temperatures overnight, leads to potential impacts. Families and friends took to the water to cool off in the River Darent in Eynsford yesterday A woman using her phone in the warm weather, in Potters Fields Park, London, yesterday The UK Health Security Agency issued amber health alerts for the south of England where they expect an increase in deaths for people aged 65 and over and people with underlying health conditions. Less serious yellow alerts are also in place in the Midlands'Temperatures will peak around the mid-30s on Monday and Tuesday. The humidity will also mean this feels close, warmer and more uncomfortable for many.'Tropical nights – where the temperature doesn't drop below 20°C – are also likely for some.'The warmth may bring some thundery downpours for some on Monday and Tuesday, though these should be 'fairly isolated', the Met Office said.The very high temperatures could continue across a smaller part of the country into the middle of the week, but this remains uncertain for now, the forecaster added.In light of the 15 deaths during the last heatwave, Samantha Hughes, national water safety partner at the Royal National Lifeboat Institution, said: 'With warmer weather approaching, it's important to remember that the water is still cold.'Entering it unexpectedly can lead to cold water shock, causing a sudden increase in breathing and heart rate, which may trigger panic.'After the heat health alerts were issued, the Health and Safety Executive (HSE) said employers must ensure their workers are protected while maintaining productivity during the heatwave.