A grieving mother whose son drowned has today warned sunseekers not to risk their lives in open water as Brits braced for a scorching heatwave . Forecasters predict the mercury will top 38C this week - marking the hottest June day on record. A stifling amber extreme heat warning has been issued for most of southern England, the Midlands and east Wales. The UK Health Security Agency also issued separate heat health alerts across large swathes of England. The stifling heat could spark delays and