Several parts of the UK are under a national emergency after a red extreme heat warning was issued as temperatures could hit 40C (104F).

The Met Office’s highest warning is spread to an area including London, Manchester and York on Monday and Tuesday. Authorities warned of the risk to life and daily routine disruption. 

The UK Health Security Agency also issued its highest level 4 heat alert to healthcare bodies – warning that illness and death could occur “among the fit and healthy.” On Friday, NHS warned there would be greater demand for ambulances amid the hot weather.

Downing Street said the alert was being treated as a national emergency.

Also Read | Why is UK experiencing a heatwave?

Heatwaves can be a severe threat to public health as they result in heatstroke and dehydration among the main risks, particularly  affecting young children and elderly people. 

Dr Laurence Wainwright of the University of Oxford said  heatwaves can have a significant impact on mental health as well. There are “positive associations between daily high temperatures and suicide,” he said.

According to Dr Michael Byrne of the University of St Andrews, the current heatwave is a dangerous reminder of the increasing impacts of global warming. It is believed that London is expected to feel like Barcelona by 2050. Byrne told the Guardian that UK is braced for more frequent and severe heat waves over the coming years.

The adverse health effects due to heatwaves include sunburn, heat exhaustion and other heat-related illnesses. Failure of heat-sensitive equipment may also occur. Loss of electricity, water supplies and gas is also possible. There could also be a disruption to travel, further leading to heavy traffic and queues. 

Also Read | Officials declare national emergency for the United Kingdom over severe heatwave

There is also an increased risk of water safety incidents due to the heatwaves. The UK experienced heatwave conditions lasting 10 days in August 2003, which claimed 2,000 lives. At the time, Faversham in Kent recorded a maximum temperature of 38.5 degrees Celsius.