What is a heatwave? London set to bask in 32C temperatures this week

The Met Office has forecast “very warm, locally hot weather” for the capital in the coming days. Tuesday could be the hottest day of the year so far, as temperatures could reach 32C.

The forecaster has predicted continuous sunshine until Friday evening, with temperatures remaining in the high 20s throughout the week.

The warm surge is due to a wave of high pressure across the country and warm air rising from the south, creating dry, fine and sunny conditions and bringing temperatures up.

Simon Partridge, a forecaster at the Met Office, said: “There is certainly potential that it could become an actual official heatwave because in the spells you’ve had before it hasn’t actually met all the criteria.

“If there’s not, it’s very close to it and if you’re out and about and a member of the public then it’s going to feel like a heatwave anyway, because also overnight things are going to turn a little bit more humid and muggy day on day as well.”

So with what might well be a heatwave in the capital on the way, what is the technical definition?

An official UK heatwave takes place when a location records at least three consecutive days with daily maximum temperatures meeting or exceeding the heatwave temperature threshold.

This varies across the country and in London that temperature is 28C.

The Met Office says heatwaves are primarily caused by prolonged high-pressure systems, also known as anticyclones. These systems create a dome of heat that traps warm air in a particular region. The high pressure suppresses cloud formation and precipitation, leading to clear skies and increased sunlight, which raise temperatures further.

Another contributing factor is the position and strength of the jet stream. When this becomes weaker or shifts its usual path, it can lead to stagnant weather patterns, allowing the high-pressure system to remain over an area for an extended period.

Additionally, heatwaves can be exacerbated by the urban heat island effect, which makes cities hotter than surrounding areas due to human activities and built-up surfaces.

While hot weather offers many opportunities for fun in the sun, it can also pose challenges for people trying to be productive.

As well as ensuring you have a fan, here are your rights when working in the heat.

There is no legal maximum working temperature specified by law in the UK. However, employers have a legal duty to ensure their employees’ health, safety and welfare at work, including managing the temperature in the workplace.

Employers in the UK have a legal duty under the Health and Safety at Work Act to ensure their employees’ health, safety and welfare. This includes providing a comfortable working environment, particularly when temperatures are high. According to the Workplace (Health, Safety and Welfare) Regulations 1992, the temperature in all indoor workplaces should be reasonable during working hours.

If the office becomes too hot, the Health and Safety Executive (HSE) advises employers to take action to reduce the temperature or mitigate its effects on employees. The Union of Shop, Distributive and Allied Workers (Usdaw) and the Trades Union Congress (TUC) have advocated a legal maximum indoor temperature to provide clear guidelines for employers and workers on when action should be taken.

Usdaw specifically recommends implementing cooling measures when the workplace temperature reaches 24C. This includes ensuring there is air conditioning, adequate ventilation and cooling drinks and breaks. The TUC underscores the importance of employers assessing risks associated with high temperatures and implementing necessary measures to manage or prevent these risks.

Usdaw suggests opening windows, using fans, allowing more frequent breaks, relaxing dress codes and adjusting policies on face coverings. If these measures prove insufficient and the workplace remains uncomfortably hot, employers should consider whether employees can work in those conditions.

In the UK, if your working environment becomes unreasonably hot and poses a health risk, you have the right to stop working to protect yourself. This is based on the principle that employers must provide a safe working environment under the Health and Safety at Work Act.

If you cannot work from home or make adjustments to mitigate the heat, such as cooling measures, and you believe continuing to work would endanger your health, you are within your rights to cease work.

If your employer penalises you if you stop working due to excessive heat – such as by taking disciplinary action or reducing your pay – you can make a claim at an employment tribunal. The law protects employees from retaliation for raising health and safety concerns or refusing to work in unsafe conditions, including extreme heat that could harm their wellbeing.

Working outdoors during very high temperatures can significantly strain the body. Usdaw says employers should ensure that outdoor workers have adequate sun and heat protection. This includes access to shade whenever possible to help workers cool down.

Additionally, employers should supply sun cream for skin protection, appropriate clothing to shield themselves from the sun’s rays, and ample drinking water to prevent dehydration. These measures are crucial for safeguarding outdoor workers’ during intense heat.