- Britain is enjoying the hottest September day since 1911 as mercury soars to record-breaking 94F (34.4C)
- Record temperature was recorded at London Heathrow this lunchtime as UK's Indian Summer continues
- Warm air is sweeping across the sea from Spain - making parts of Britain hotter than Thailand and LA today
- Public Health England is warning of dangers to children, the elderly and those with underlying health issues
Today has officially become the hottest day of the year so far and the warmest September day in 105 years after temperatures soared to a scorching 34.4C (93.9F) - despite parts of the UK enduring heavy rain and lightning.
Sunseekers have flocked to parks and beaches across the country to make the most of the flash heatwave which has seen the mercury rise to a record-breaking 34.4C at Gravesend, Kent and 32.8C at Heathrow, London.
Forecasters say large swathes of southern England and the Midlands are also enjoying temperatures of 31C and '32C in places' - meaning parts of the UK are currently warmer than Rome, Crete, Thailand, Majorca and Madrid.
However, other areas of the UK including Wales and parts of the South West are enduring driving rain and thunder. Dramatic pictures show lashings of rain battering seafronts in Swansea and Bournemouth - a stark contrast to those which show sunbathers lapping up the rays just a little further along the coast in the South East.
The record-breaking high temperatures in the capital and South East today are unusual for this time of the year with experts saying the mercury only hits the 30s in the month of September 'once or twice every 100 years'.
The 34.4C recorded in Gravesend today smashes the current record for the hottest September day, which was recorded as 34.6C at Raunds, Northamptonshire in September 1911.
It also makes today the hottest day of 2016, beating the 34.1C recorded at Faversham, Kent on August 25.
Feeling hot, hot, hot! Two women were seen relaxing in their bikinis in London's Hyde Park by lunchtime as temperatures soared to record-breaking highs. The Met Office said 32.8C had been recorded at London Heathrow by about midday
Kicking back: One woman was topping up her tan in Hyde Park, London, at lunchtime as the mercury soared towards a balmy 32C. The high temperatures are unusual for this time of the year with forecasters it happens 'once or twice every 100 years'
Time for a snooze? One man appeared to try and catch 40 winks on a bench overlooking the Serpentine at Hyde Park in central London at lunchtime today as the capital and the south east enjoyed the best of the Indian Summer heatwave
A different kind of morning commute: Workers enjoyed a bit more sunshine than they are used to as they made their way to the office in the capital this morning including on South Bank (pictured) where water fountains were keeping the grass damp
What a difference: While those in the south east were basking in record-breaking temperatures this lunchtime, residents in Bournemouth, Dorset (left) and Swansea, Wales (right) were enduring thundery showers as a band of rain swept in
Forecasters say the mercury will widely reach 31C across much of southern England but parts of the south east and London will see 32C by this afternoon. Pictured: This Met Desk graphic shows the areas that will see the hottest temperatures today
Earlier today, the Met Office said Heathrow and Kew Gardens, west London, recorded a temperature of 32.8C.
The last time temperatures soared above 30C (86F) in September was in 2006 in Kew Gardens, which hit 30.5C (87F) on September 11.
The highest September temperature rver recorded was in 1906 when the mercury hit 35.6C (96.1F) in Bawtry, South Yorkshire.
Grahame Madge, a Met Office spokesman, said: 'Temperatures in the South East have created the warmest September day in the UK since 1911.
'However, not all parts of the UK have been so warm. Parts of Scotland, such as Lossiemouth, and Northern Ireland have struggled to get beyond 14C.
'We are not likely to see a repeat on Wednesday as we expect temperatures to have peaked today. Toward the end of the week we will see temperatures cool down on Friday as fresher air from the Atlantic pushes across the UK.'
ITV forecaster Lucy Verasamy joked: 'This September is showing off.'
Forecaster Mark Wilson told MailOnline: '[Today] is a very hot day and that warmth is spreading right across the bulk of the country. We're seeing highs of 31C widely in the East of England.
'It will be warm across the rest of the country too, even reaching 24C and 25C on the Scottish borders.'
The Met Office added that the London region was 'most prone' to getting the highs of 32C-34C today, as well as parts of the 'South East corner'.
One fine day: Dog walkers and joggers were out in full force this morning in Hyde Park as they tried to make the most of the scorching heatwave in the capital. Forecasters confirmed the mercury reached a record-breaking 32C in London by lunch
Enjoying the late summer: One man indulged in a good book as he kicked back in a bright Hyde Park, London, this lunchtime
Time for a dip: One couple enjoyed a swim in the sea at Bournemouth, Dorset before the rain swept in from the west today
Calm before the storm: A woman enjoyed reading her book in the sunshine in Bournemouth, Dorset, before the rain hit today
Stormy: A bolt of lightning is seen over the sea at Bournemouth, Dorset as the wet weather from the west moves in
Indian Summer: The warmer air will move up from France and Spain - bringing balmy temperatures to Britain today
The flash heatwave has prompted Public Health England (PHE) to issue a string of health warnings amid fears for children, the elderly and those with underlying health conditions.
Dr Thomas Waite, from the extreme events team at PHE, said: 'For some people, such as older people, those with underlying health conditions and those with young children, summer heat can bring real health risks.
'The hot weather won't make life difficult for all of us; indeed, many of us will make the most of it when the sun shines. But some people may not be able to adapt to the extra strain hot weather will put on their bodies and may feel the ill-effects.
'Each year we hear stories of people who have fallen seriously ill because, even though it's hotter, they may wear clothes which are too warm for hot weather, they may not drink enough or just try to do too much.'
It has also caused problems for motorists and train passengers, with the warm weather causing a host of issues.
The RAC said newly-laid roads had started to melt and estimated around 30,000 breakdowns today alone.
RAC spokesman Pete Williams said: 'Tarmac which is newly-laid is going soft, so motorists should be careful.'
Thousands of rail commuters also face delays after speed restrictions were imposed on amid fears the train tracks could buckle.
Greater Anglia said: 'Due to a speed restriction because of high temperatures between Stratford and Southend Victoria, trains have to run at reduced speed.' Network Rail added: 'Rails expand as they heat up. Slower trains exert lower forces and reduce the chance of buckling.'
A stunning skyline: St Paul's Cathedral, the Walkie Talkie and the 'Cheesegrater' building basking in the sunshine in London
What a view: There were stunning scenes at Bournemouth beach this morning as the morning sunrise created pretty skies
Out in the countryside: A misty sunrise over a field just north or Leeds, West Yorkshire, as temperatures soar towards 32C
Could it be the hottest September day? A misty sunrise over Golden Acre Park, in Leeds, West Yorkshire ahead of the sun
Met Office forecaster Simon Partridge said the heatwave has been caused by hot air coming from the south.
He said: 'The origins of this air is generally southern France and northern Spain, where things are fairly warm at this time of the year. So we'll start to see things warming up.'
Despite the balmy conditions across much of the south of England, rain has been lashing the West and Wales.
Health warnings were issued ahead of what is now confirmed as the hottest September day in decades, but severe weather warnings of rain are now in place for Northern England and South East Scotland.
Outbreaks of rain may turn torrential and thundery, with as much as one inch (30cm) falling in some places, possibly causing flash flooding and disruption to travel. The yellow warnings are valid from 2pm to 11pm today.
Forecaster Mr Wilson said: 'It's going to be a hot day but it will be cooling off in the evening.
'In the west and parts of Wales we seeing thundery showers which will spread northwards into North West England but elsewhere it's going to be dry overnight. It could be very warm and muggy and quite uncomfortable in the evening tonight'.
A beautiful morning: A jogger runs through early morning mist on low-lying ground next to the River Thames near Windsor Castle at the start of what has been confirmed as the hottest September day in more than 70 years - beating the 1949 record
Breaking through the clouds: The sun was trying to make its way through the light haze in Eton, Berkshire early this morning
Morning sunrise: Cormorants on a pier at North Shields Fish Quay as the sun rises ahead of another scorching day in the UK
Mr Wilson added that conditions will become more unsettled on Friday when a band of rain will sweep eastwards and 'fresher' air coming in from the Atlantic sees temperatures tumble.
He said: 'Tomorrow will be pretty decent but it's not going to be as hot as it will be today. Temperatures could reach 28C tomorrow in the South East, which is a couple of degrees cooler but still very warm.
'However, on Friday we see a drop in temperature and the wind direction changes so we go back to average temperatures for this time of year.'
The following week will split the UK, with the North West experiencing rain interspersed with dry spells, while higher pressure over Europe brings drier, warmer and more settled weather to the South East.