The Met Office had extended its extreme heat weather warning beyond the weekend, warning of potential serious illness or danger to life.
A rare amber alert for extreme heat was yesterday issued for large parts of the UK for Sunday which could set a new temperature record.
Forecasters at the Met Office have now extended the warning into Monday as Brits face baking conditions with the mercury possibly nudging above 40C - temperatures usually experienced in the likes of Death Valley in the US.
They warned "substantial" changes will be required for working practices and daily routines to keep people safe in the extreme conditions.
The East Midlands, East of England, South East England, North East England, North West England, South West England, Wales, West Midlands and Yorkshire & Humber are under the warning for extreme heat.
The Met Office's warning reads: "Exceptionally high temperatures are possible during Sunday and Monday and could lead to widespread impacts on people and infrastructure.
"What to expect: Population-wide adverse health effects are likely to be experienced, not limited to those most vulnerable to extreme heat, leading to potential serious illness or danger to life.
"Government advice is that 999 services should be used in emergencies only; seek advice from 111 if you need non-emergency health advice."
They added there is a significant risk to those in coastal areas, lakes and rivers because of an increased risk of water safety accidents, forecasters said.
Some reports have suggested Brits could swelter in 43C heat next Sunday, although the Met Office warned this exact figure is "very unlikely".
Today Brits are set for another scorching day with highs of 32C sparking advice about how to keep cool.
High temperatures are coming from hot air moving north from Africa, passing through Spain and France with the mercury reaching 32C in Northolt, West London, on Monday.
After a very stuffy night with the temperatures remaining warm, it is expected to be hot again today and reach 32C in the South East.
There is though a weather front that will bring cloud and some rain for the north of the UK.
Met Office forecaster Alex Deakin: "A very different day for Scotland and Northern Ireland, certainly some cloud here early on with some outbreaks of rain drifting through the central belt and spreading across Northern Ireland, nothing too heavy but certainly a change compared to Monday."
Yesterday it was so so hot even the train tracks burst into flames.
Train services had to be suspended this morning after a fire on a bridge in Battersea, South London, between Victoria and Brixton.
