Britain faces more drowning deaths and a 'risk to life' as the third heatwave of the year begins this weekend, after the country's hottest May and June days on record.The UK Health Security Agency (UKHSA) has issued a yellow health alert for southern and eastern England and the East Midlands from Saturday until Wednesday.The five-day alert warns of 'greater risk to life of vulnerable people' and that 'water‑ related incidents may increase, including risks from cold water shock and drowning'.The heatwave could also bring 'increased use of healthcare services by vulnerable people' and 'increased potential for indoor environments to become very warm'.Health officials fear further deaths after at least 11 people died in water-related incidents during the June heatwave – on top of the 17 during the May heatwave.On Monday afternoon, following the end of the latest heatwave, a 13-year-old boy died after being pulled out of open water at Royal Victoria Dock in east London.Emergency services were called to reports of a child in the water just after 4pm, and first responders recovered him but he was pronounced dead at the scene.Temperatures for the rest of this week are expected to be just below the heatwave threshold, with highs in London of 26C today and tomorrow and 27C on Friday. Standup paddleboarders at Lulworth Cove in Dorset yesterday as the warm weather continues The UK Health Security Agency issued a yellow heat health alert from Saturday to Wednesday The forecast for London suggests the heatwave threshold of 28C will be met from SaturdayBut the 28C threshold is expected to be met in the capital on Saturday, before the mercury rises further to 29C on Sunday, 31C on Monday and 30C on Tuesday.The Met Office says a heatwave is defined as three consecutive days with daily maximum temperatures meeting or exceeding the heatwave temperature threshold.The threshold varies across the UK – between 25C in Scotland, Northern Ireland, Wales and south-west England, and 28C in London and its surrounding counties.Given at least 28C is forecast in London for four days in a row from Saturday to next Tuesday, the UK would officially re-enter heatwave conditions by Monday. TOP TEN HOTTEST DAYS IN BRITAIN - INCLUDING TWO LAST WEEK 1 40.3C July 19, 2022 Coningsby, Lincolnshire 2 38.7C July 25, 2019 Cambridge 3 38.5C August 10, 2003 Faversham, Kent 4 38.2C July 18, 2022 Pitsford, Northamptonshire 5 37.8C July 31, 2020 London Heathrow 6 37.7C June 26, 2026 Lingwood, Norfolk 7 37.1C August 3, 1990 Cheltenham, Gloucestershire 8= 36.7C August 9, 1911 Raunds, Northamptonshire 8= 36.7C July 1, 2015 London Heathrow 8= 36.7C June 25, 2026 Merryfield, Somerset Met Office deputy chief forecaster Tony Wisson said: 'Towards the weekend, high pressure will continue to build in across most of the UK as it extends from the Azores.'This will lead to more settled, warm or very warm conditions for many, especially across England and Wales, though some rain may still affect the far north.'The forecast for this weekend suggests that temperatures could approach high 20s across parts of England, perhaps 30C in parts of the South East, with values of mid to high 20s in Wales.'Although a return to heatwave conditions is looking increasingly likely for some areas, the likelihood of such extreme high temperatures or high levels of humidity as last week is currently low.'Today, wet and windy weather will spread into parts of Scotland and Northern Ireland later on after yellow warnings for rain and thunderstorms were issued yesterday.But England and Wales can expect largely dry conditions with sunny spells breaking through the cloud today, bringing highs of 26C to the South and 24C to the North.The Met Office revealed on Monday that a new provisional June temperature record of nearly 38C was set last Friday – even higher than previously thought. The heatwave threshold is defined as three consecutive days at or above a set temperatureAn updated high received by the weather service over the weekend of 37.7C at Lingwood in Norfolk was above the 37.3C recorded at Santon Downham in Suffolk last Friday, which had been announced on the day as the all-time June high.The new record during the exceptional heatwave which prompted a rare red 'danger to life' warning beats the previous June record of 35.6C dating back to 1976 by 2.1C.The June temperature record was broken three days in a row last week as thousands of schools closed, ambulances had record callouts, trains were cancelled, hospitals declared critical incidents and there was a South East Water hosepipe ban in Kent.The country also recorded two of its top ten hottest days on record – one being the 37.7C and the other being a 36.7C high at Merryfield in Somerset last Thursday.The Met Office said last month was England's warmest June in records going back to 1884, while the UK as a whole and Wales recorded their second warmest June.In England, a provisional mean of 17.1C was recorded for the month, surpassing the previous record set in 2025 and nearly 3C above the long-term average.The forecaster said 'exceptionally warm overnight temperatures' during the latest heatwave helped to 'drive the highest average minimum temperatures on record for the UK, England and Wales'.For the UK, June 2026 provisionally ranks as the second warmest June on record, behind only June 2023. Wales recorded its second warmest, while Scotland and Northern Ireland both saw their joint fourth warmest June since 1884.The June heatwave came four weeks after England and Wales each recorded their hottest ever day in May with highs of 35.1C and 32.9C respectively. The UK had four heatwaves in 2025 – two in June, one in July and one in August. The country's highest temperature last year was 35.8C at Faversham in Kent on July 1.