Record temperatures have been forecast for this week, with some weather experts predicting scorching highs of 37C in parts of the country.
Thursday is set to be the hottest day of the year so far - and the Met Office believes "an all-time maximum temperature for July" could be set.
And it looks like the roasting conditions are here to stay for the summer as meteorologists suggest the heatwave could last for six weeks until the end of August.
But how hot must it get before employees can leave work?
There are currently no laws in England, Scotland, Wales and Northern Ireland concerning when it is too hot to work.
The Health and Safety Executive notes this is because limits cannot be set due to certain jobs requiring workers - foundries, for example - to operate in high temperatures.
An employer must provide a working environment which is, as far as is reasonably practical, safe and without risks to health.
However, union reps have explained that workers are allowed to leave the workplace if temperatures are no longer "reasonable" - and have offered guidance on what that means.
The TUC advises the sweltering heat could become a health and safety matter, with workers risking dizziness, fainting, cramps - and maybe even heat stroke.
"An employer must provide a working environment which is, as far as is reasonably practical, safe and without risks to health.
"In addition, employers have to assess risks and introduce any necessary prevention or control measures," it states.
Furthermore, it is possible to prompt such assessments if workers come together to express their discomfort.
"If a significant number of employees are complaining about thermal discomfort, your employer should carry out a risk assessment, and act on the results of that assessment," the HSE explains.
Heading out this afternoon? #Sunny and #hot across most parts of the UK, so grab your water and sun cream and remember to seek shade through the middle part of the day #Heatwave #HeatwaveUK pic.twitter.com/rTPCwDWbMH
— Met Office (@metoffice) July 23, 2019
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