The Met Office issues a rare red warning for extreme heat, covering parts of Hampshire, Dorset, Berkshire and Oxfordshire.
It comes into place at 09:00 on Wednesday and will last until 21:00 the following day.
Schools in Hampshire, Berkshire and Oxfordshire have announced closures and reduced hours due to the heat.
There is a warning about the potential for wildfires in Dorset.
Train companies have responded to heat warnings by running amended timetables.
Follow this advice to keep yourself and your home as cool as possible.
Weather forecast for the south of England
Tuesday will see exceptionally hot and humid conditions under sunny skies and a gentle south-easterly breeze.
A few isolated patches of cloud may occasionally drift by through the day.
Image source, Oxfordshire County CouncilOn Wednesday and Thursday waste and recycling centres in Oxfordshire will open at 08:00 and close early at 13:00 BST due to the high temperatures.
Oxfordshire Recycles, external said: "Thanks to the booking system, we have been able to notify those who had booked a slot, saving any wasted journeys as a result of this early closure.
"Those who had bookings have been invited to rebook their visit for an alternative time."
Image source, ReutersSchools in Hampshire, Berkshire and Oxfordshire and Dorset have announced closures and reduced hours due to the heat.
Schools usually contact parents in their own ways, often through apps or messaging services.
Hampshire County Council, external and West Berkshire Council, external post a list of reported emergency closures.
A list of schools that have had to close suddenly is also posted on the Oxfordshire County Council website, external. The council said it relies on schools to tell it when they are closed.
Image source, BBC Weather Watcher SlimThe highest overnight temperature was 20.4C in Gosport.
The Met Office said eight other places including Hurn in Dorset and the Isle of Wight recorded a tropical night - where temperatures did not fall below 20C.
Image source, ReutersHomes and businesses in parts of Witney, Oxfordshire are facing disruption to their water supplies.
A burst pipe at Poffley End means those in the OX29 postcode area have no water or low pressure.
Apologising Thames Water , externalsaid: "We're currently working to isolate this burst pipe and will be able to begin repairs shortly after."
The water firm said it hoped to have an update by 11:00 BST.
The UK is likely to experience its hottest June day on record on Tuesday with temperatures forecast to rise above 35C (95F).
The highest June temperature on record of 35.6C was set on 29 June 1957 at Camden Square in London, then equalled on 28 June 1976 at Mayflower Park in Southampton.
You can find out more about the 1976 heatwave in the South here.
Image source, Getty Images
Darren Paffey MP has issued a water safety plea
A Southampton MP has urged parents to talk to their children and teenagers about safety in the water as temperatures soar.
The Labour MP for Southampton Itchen, Darren Paffey, led a Parliamentary debate on water safety education earlier this month following recent drownings, including several in the south.
He said such incidents were "a stark reminder that we cannot afford to take risks or assume that everyone knows what to do in an emergency”.
He added: “These may feel like simple messages, but knowing them could make the difference in an emergency. A short conversation around the dinner table today may well save a life tomorrow.
“Please enjoy the water and everything our waterfront city has to offer this summer, but please do so safely.”
Image source, SWRSouth Western Railway (SWR) will run an amended timetable from today and is urging people to only travel if essential on Wednesday and Thursday.
On all three days, fewer trains are set to run across the SWR network. Trains that run are expected to be busier and journey times will likely be longer than usual, as trains run at reduced speeds.
SWR said it plans to update journey planners with the amended timetable for Wednesday and Thursday at 02:00 on Wednesday morning.
The rail firm is urging people to check its website for the latest travel advice, external and ticket information before setting off
Indy Almroth-Wright
BBC South
Image source, BBC Weather Watcher Katie JadeIt’s already a warm start this morning, and temperatures will keep rising.
Let's bring you up to speed:
A Met Office red warning, external for extreme heat will be in place from 09:00 BST on Wednesday to 21:00 on Thursday in parts of Oxfordshire, Berkshire and Hampshire.
An amber warning is already in force across a wider area until Thursday.
Schools in Oxfordshire, Berkshire and Hampshire are closing or finishing early this week because of the extreme heat.
National Rail is advising people to only travel if absolutely necessary on Wednesday and Thursday.
That's the end of our live page for today, but we'll be back in the morning to bring you updates after the Met Office issued a rare red warning for heat for parts of the region.
An additional amber warning for extreme heat still remains in force across much of our patch.
Time for heatwave sleep tips?
Hope you get a good night's sleep.
Image source, Met OfficeA reminder that a red warning for extreme heat comes into force at 09:00 on Wednesday until 21:00 on Thursday, covering Oxfordshire, Berkshire, Hampshire and Dorset.
It's the most serious level the Met Office issues, meaning a high likelihood of danger to life and risk to power and transport.
Temperatures could reach 38-39C as the red warning takes hold.
Amber warnings will remain in force across a wider area from now until Thursday.
Dorset Council has said it is working with partners Alongside (formerly Julian House) and the Lantern Trust to support people sleeping rough during the hot weather.
Sophie Cridland
BBC South
The Frampton Arms in Moreton, Dorset is asking customers to be patient because the kitchen staff will be taking regular breaks.
On social media it posted that the kitchen could sometimes get 15 to 20 degrees warmer than it is outside.
“This might mean a short wait now and then, but we promise we’re working hard to look after both you and our crew.
“We will be watching the temperature closely throughout the week and we might have to make the tough decision to close the kitchen slightly earlier,” it added.
Hampshire County Council says it has contacted schools to share "general advice" on how to keep buildings and students cool.
But it added that whilst schools were "not normally expected to close in hot weather", each individual one is responsible for making a decision.
Image source, Chiltern RailwaysChiltern Railways passengers are being advised not to travel over the coming days
Chiltern Railways has said people should avoid travelling during the heat wave.
It said "significant disruption" to services was anticipated until Friday due to the extreme heat.
Michael Stewart, from the railway firm, said its trains would be running at "greatly reduced levels to ensure everyone's safety", meaning passengers may experience "significant delays and very busy conditions".
Sophie Cridland
BBC South
South Western Ambulance Service is warning people to stay out of the sun and drink plenty of water.
The NHS trust said it was already seeing an increase in activity across the region and on Sunday dealt with 9.5% more incidents than expected for this time of year.
Wayne Darch, director of operations, said: “We are receiving calls that could be managed through self-care, pharmacies, NHS 111 online or other healthcare services.
“Every less urgent 999 call reduces our ability to respond quickly to patients facing life-threatening situations.”
Image source, Getty ImagesSchools across the south have announced closures or ammended timetables after the Met Office issued a red weather warning for extreme heat across much of the region.
Alongside those already announced, Maiden Erlegh Trust has said it's schools across Berkshire will close at 13:30 BST on Tuesday and not reopen until Friday.
Explaining the decision in a letter to parents, Maiden Erlegh School headteacher Steve Jupp said: "While we appreciate the inconvenience that short-notice closures may cause for families, the health and safety of students and staff must remain our priority."
Meanwhile, St Birinus School in Didcot said its days would be ending at 12:15 on Tuesday, Wednesday and Thursday.
In a post on its facebook page, the school said this was to "ensure everyone remains safe during these unprecedented weather condition".
Image source, Fareham Borough CouncilFareham Borough Council is urging residents to check its website and social media , externalfor updates on bin collections during this week’s hot weather.
To protect crews working in high temperatures and keep services running, the council said collections will start earlier than usual from Tuesday 23 June.
Residents are asked to put their bins out earlier, ideally the night before their usual collection day.
Image source, Philip JoyceIt’s not just humans trying to keep cool during the heat wave.
Creative keepers at Oxfordshire’s Cotswold Wildlife Park have been providing frozen treats to the animals, from the smallest – Mabel, a pygmy marmoset – to the tallest – its tower of giraffes.
Assistant animal manager Chris Kibbey explained that the treats were made specifically for each animal’s diet.
Image source, Philip Joyce“The lemurs were treated to lollies made from blended cucumber and pear and the bamboo lemurs had a healthy blend of cucumber and celery.
“The larger animals weren’t left out, with the camels being given a frozen cocktail of carrot, cabbage, watermelon and apple and the giraffes received carrot, cabbage and apple,” he added.
George the giant tortoise, the park's oldest resident at 90, also enjoyed a cool shower thanks to staff.
Image source, Phillip Joyce
Image source, Philip Joyce
Image source, The Henry Box SchoolThe Henry Box School in Witney will close on Wednesday
Schools across Oxfordshire and Hampshire have closures and early finishes this week due to extreme heat.
Headteachers have cited concerns over the safety and the comfort of pupils and staff, with some schools relaxing uniform rules and adding extra water stations as well as cutting the day short.
Education reporter Vanessa Clarke said the government does not normally advise schools to close, and that most of the time the heat can be managed safely.
But she said schools are expected to adapt to keep pupils safe and comfortable, with many already relaxing uniform rules and asking children to bring sunscreen and sun hats.
"Older school buildings, which can be harder to keep cool, will often have had staff in early opening doors and windows to keep air moving," she added.
Guidance from the UK Health Security Agency says schools may need to close their windows later in the day if it becomes hotter outside than in, and that fans should not be used once temperatures pass 35°C.
Lessons may be moved to cooler parts of a school, and hot meals could be swapped for cooler options. Some schools may also change their start and finish times to avoid the worst of the heat.
Oxfordshire
The Henry Box School, a secondary school in Witney, will close at 11:30 BST on Wednesday.
In a letter to parents, headteacher Wendy Hemmingsley highlighted the warnings issued by the Met Office and said the safety of students and staff is the school's "highest priority".
She said rising temperatures can make learning environments "increasingly uncomfortable".
Outside of the closure, Hemmingsley said students could wear PE kits to help keep cool and said the school was installing additional water stations around the building.
Ducklington Primary School has announced a closure from 13:15 on Tuesday and said it would consider its position regarding the rest of the week.
Hampshire
Eggar's School in Alton is closing from 13:00 on Tuesday, Wednesday and Thursday this week.
Grateley Primary School in Test Valley is bringing forward collection to 13:15 on Wednesday and Thursday, citing the red weather warning.
Cranbourne School in Basingstoke will close at 12:50 on Wednesday and Thursday, while Crestwood Community School, near Eastleigh, will close at 13:00 on Wednesday.
