It's the world's most famous prehistoric monument which has stood for 5,000 years.But with temperatures hitting 31C in Wiltshire today, English Heritage said Stonehenge would shut early because the conditions were unsafe for staff and visitors.This is despite the Neolithic site being located outside the amber and red extreme heat warnings issued by the Met Office today as the heatwave continues.The circle will shut at 3pm today with last entry at 1.30pm after the same early closure yesterday, 'due to the hot weather and to ensure the safety of visitors and staff'.Tourists heading to the attraction were advised to 'bring plenty of water, take breaks as needed, and consider the warm conditions if you're planning to bring your dog'.But some of those responding to the announcement by Stonehenge on Facebook were unimpressed, with one saying: 'Pathetic. Do you think the Colosseum closes when it gets past 30C?' Another wrote: 'Quit being so soft, it's summer.'Other attractions closed due to the heat in London included Tower Bridge, the Young V&A, the Cutty Sark and the Royal Observatory. Marwell Zoo in Hampshire shut, as did more than a dozen restaurants in London and some Greggs stores around the UK.It comes as Britain had its hottest June day ever for a third day in a row today with highs above 37C after spectacular lightning struck during thunderstorms last night.The Met Office said a temperature of 37.3C was recorded at Santon Downham in Suffolk - one day after a new June record of 36.7C was set yesterday in Merryfield, Somerset.That came after another new record on Wednesday of 36.1C in Gosport, Hampshire; which itself beat a longstanding June high of 35.6C dating back to summer 1976.Today was also the UK's joint sixth hottest day ever, above a 36.7C record set in 1911 in Northamptonshire, which had stood as the country's hottest day for eight decades.The Met Office confirmed temperatures were 'still rising' this afternoon – and if 38C is reached later on, that would make today the country's fifth hottest day on record.Today is also a record-breaking third consecutive day of red extreme heat warnings in the South East. A wider amber warning for the East and Midlands was also in place.London and Manchester could reach 36C today, with Belfast and Cardiff at 26C. This follows another 'tropical night' when temperatures failed to fall below 20C - with the highest overnight low in Herstmonceux, West Sussex, dropping to only 22.7C.The Government's UK Health Security Agency (UKHSA) has now extended its amber alert heat warnings until Sunday morning for the whole of England, warning of a 'rise in deaths, particularly among those aged 65 and over or with health conditions'. Thousands of schools and nurseries have shut during the heatwave - with some asking parents to pick children up early today amid soaring classroom temperatures - and a South East Water hosepipe ban was brought in for Kent amid surging demand.Trains have faced major delays with operators urging people to only make essential journeys and South Western Railway telling people not to travel for beach trips.The M5 in Somerset was shut in both directions this afternoon between junctions 22 and 23 because of a risk that overhead electricity cables could fall into the road - causing two-hour delays and eight miles of congestion in both directions. In the Solent yesterday, a yacht and a motorboat crashed into each other off the coast of Southampton - with the mariners blaming sun glare. No injuries were reported but the motorboat sustained significant damage and the yacht had minor damage. A lightning storm over Stonehenge in Wiltshire early this morning, pictured just after midnight English Heritage says Stonehenge will shut early today because of the heatwave conditions Sisters Julia (left) and Claire Bottoms at Sea Lanes Canary Wharf in east London today People fill their water bottles at a fountain during hot weather in London this afternoon Children from Grasmere School in Cumbria are taught maths, physics and water safety today A woman feels the heat as she sits in the sun at Greenwich Park in south-east London today People cool off at Warleigh Weir near Bath in Somerset today as the heatwave continues A woman crossing Westminster Bridge carries a water bottle in the sweltering heat today A woman carries a young child on the beach at Southend-on-Sea in Essex this afternoon People relax in the shade at St James's Park in central London as the hot weather continues A man holds two pints as he walks next to the River Great Ouse in Ely, Cambridgeshire, todayTourists gather outside Buckingham Palace during the extreme heat in London today A woman on Westminster Bridge takes a picture of an ice cream in the sweltering heat today People queue at a fountain at St James's Park in London to fill water bottles this morning A woman uses an electric fan to cool down on Westminster Bridge in London this afternoon People rest in the shade at a park during hot weather in London this afternoon A woman at Green Park in London shelters from the sun while using an umbrella today People fill their water bottles at a fountain during hot weather in London this afternoon Visitors to Greenwich Park in south-east London take a picture from the viewpoint today Mark Curren carries a box to his stall at North End Road Market in Fulham, west London, today Swimmers enjoy the water at Charlton Lido in south-east London during the heatwave today A woman cools herself with a handheld fan during the heatwave in Manchester this afternoon Two builders take a mid-morning break with a full English breakfast in Fulham, London, today A woman uses a fan as she makes a morning journey towards the centre of Bristol today A bus driver takes a break in the shade today as the heatwave continues in London Sunrise this morning on Glastonbury Tor in Somerset as the extreme heatwave continues