Forecasters are predicting the UK could have its hottest June day ever recorded on Friday, with temperatures expected to hit a sweltering 34C by the end of the week.
On Wednesday, parts of the South East basked in 28C of sunshine as the summer heat kicked in.
Temperatures were expected to increase further on Thursday, with predicted highs of 29C in London and the surrounding area.
On Friday, 34C is forecast in the South East along with temperatures between 27C and 30C across most of England and Wales.
Despite the hot weather, the Met Office has said it does not expect there to be an official heatwave.
A spokesperson said: “Although some parts of England may perhaps meet these heat wave criteria it looks like this spell of warm weather will be relatively short-lived.
“Milder conditions look likely to return later in the weekend with temperatures trending back to around average for June as we see cooler air push across the country from the northwest.”
What is a heatwave?
The Met Office says a UK heatwave threshold is met when a place “records a period of at least three consecutive days with daily maximum temperatures meeting or exceeding the heatwave temperature threshold”.
This threshold varies in each county.
Do I have to do work during a heatwave?
An employer decides if it’s too hot for staff to work, but bosses must maintain reasonable temperatures in the office, according to the Workplace (Health, Safety and Welfare) Regulations 1992.
The legislation does not say what maximum temperature is allowed but Trades Union Congress (TUC) is campaigning for it to be 24C in offices.
The Health and Safety Executive (HSE) recommends employees should have access to cool water.
It adds employers should also consider what clothing an employee is allowed to wear during hot temperatures and allow for changes in uniform or dress code.
If staff work outside, they would be given regular rest breaks to hydrate often.
What weather alerts and warnings can Met Office issue for a heatwave?
The Met Office has issued a level 2 heat-health alert for a large part of southern and central England from Friday until midnight on Sunday, with a level 1 alert in place for northern England.
On the four-level heat-health alert scale, designed to help healthcare workers manage through periods of extreme temperatures, level 1 is the lowest warning and is the minimum state of vigilance used during the summer months.
Level 2, called alert and readiness, is triggered as soon there is a 60% risk that temperature thresholds will be reached in one or more regions on at least two consecutive days and the intervening night.
The Met Office also issues weather warnings in three colours (yellow, amber or red) depending on the severity.
They cover rain, thunderstorms, wind, snow, lightning, ice, extreme heat and fog.
When making the decision, it considers the impact the weather may have and the likelihood of those impacts occurring.
Tips on handling the hot weather
First aid and health response charity St John Ambulance has issued some tips for handling hot weather.
Its medical director Dr Lynn Thomas said: “If you’re out and about in the sunshine, it’s important to make sure you look after yourself by staying hydrated, keeping out of the sun at peak times, and by wearing sunscreen with a minimum SPF 30.
“I would also encourage anyone with elderly relatives and neighbours to check in with them, as any increase in temperature can be dangerous.”