It's about to get hot, very hot with temperatures forecast to hit 35C this week in parts of London.

So inevitably the question on many people’s dry parched lips will be how warm does it have to be before we’re allowed to go home from work?

Unfortunately the answer isn’t very good for anyone hoping to get more than just their lunch break to escape the office and do some sunbathing.

This is where the law stands on temperatures in the workplace and whether it is too hot to work ...

The Health and Safety Executive’s guidance has previously defined thermal comfort in the workplace as: "An acceptable zone of thermal comfort roughly between 13°C (56°F) and 30°C (86°F)."

The temperature in workrooms should normally be at least 16°C, or 13°C if the work is manual labour, but there is no upper limit.

Although there is no set maximum temperature for when it is too hot to work, the law states that employers must provide a “reasonable” temperature.

READ MORE: London prepares for highs of 30C as 'heatwave' looms

Workers are advised to tell their employer if the workplace temperature is not comfortable.

HSE guidance also states that your employer may need to consider carrying out a "thermal comfort risk assessment" if a significant number of people complain of being too hot.

The Trades Union Congress has previously called for employers to temporarily relax their dress codes so staff can breeze through the heatwave.

Employers can still demand their staff to dress in a particular way, no matter the weather or the temperature, as uniform or clothing expectations are often included in a contract of employment but the TUC has advised employers to allow staff to adopt less formal attire.

It also recommends fans be distributed, and staff be provided with a ready supply of cool drinks.

Where people are working outdoors, employers should consider reviewing working times so that, where possible, work is done in the morning and afternoon, rather than around midday when temperatures are highest, it says.