Heat-health alerts have been issued across all of England, as temperatures are expected to rise towards 32C (89.6F).
The alert service warns the public when high temperatures could damage their health.
How does the heat health alert system work?
Run by the UK Health Security Agency (UKHSA) and the Met Office, the heat-health alert system (HHA) was introduced in June 2023.
It issues warnings to members of the public and sends guidance directly to NHS England, the government and other healthcare professionals.
The alerts are categorised according to severity and include:
headline weather conditions expected in the coming days
details of how weather conditions will affect each region
links to additional information, advice and guidance.
The hottest 10 years on record have all taken place in the last two decade, and the Met Office predicts 2023 will be hotter than 2022.
It is hoped the system will help reduce illness and deaths.
Dr Matt Patterson at the University of Oxford told the BBC: "The HHA is a tool to better communicate upcoming risks to decision-makers in the health service and to allow them to prepare".
"The UK is going to continue to warm as the world continues to burn fossil fuels. We need to update our infrastructure to help people cope with our warming climate," he said.
A report by the independent Committee on Climate Change said that England was not ready for the unavoidable impacts of global warming.
What does each level mean?
The level of alert is based on Met Office forecasts and data.
There are four levels ranging from green (least severe) to red (most severe):
Green is the normal level, when advice is given on how people should prepare to respond if temperatures rise.
Yellow alerts are issued during periods of hot weather that are only likely to affect those who are particularly vulnerable, for example, the elderly or those with existing health conditions.
Amber alerts are issued in situations that could potentially put the whole population at risk. The NHS may see increased demand on GPs and ambulances, for example.
Travel disruption would also be likely.
A red alert is the most severe.
It is issued in situations where the hot weather would be a significant risk to life for even the healthy population and could lead to failures of critical national infrastructure, such as power outages or roads and rail lines being closed.
If the alert system had been in place when the UK hit 40C in 2022, there would probably have been an alert in this category.
Which areas are covered by the latest alert?
the South East
the South West
the East Midlands
the West Midlands
the North West
Yorkshire and Humber
A yellow warning remains in the North East.
Hot conditions are also expected in Wales, while parts of Scotland and Northern Ireland could see "unseasonably high temperatures".
How can I sign up for alerts?
You can sign up to receive both heat-health alerts and cold-health alerts on the UKHSA website.