Nine regions of England have been issued with a yellow weather-health alerts as temperatures are expected to soar to 30C today.
Most of England is subject to the alerts, circulated by Met Office and UK Health Security Agency (UKHSA).
It will, however, be warmest across Southern England today.
Writing on UKHSA's website, it and Met Office says: "Significant impacts are possible across the health and social care sector due to the high temperatures, including: observed increase of mortality across the population, particularly in the 65+ age group or those with health conditions, but impacts may also be seen in younger age groups.
"Increased demand for remote health care services is likely; internal temperatures in care settings (hospitals and care homes) may exceed recommended threshold for clinical risk assessment; impact on ability of services to be delivered due to heat effects on workforce possible and many indoor environments likely to be overheating, risk to vulnerable people living independently in the community as well as in care settings."
Full list of regions issued with yellow weather-health alerts
- East Midlands
- East of England
- London
- North East
- North West
- South East
- South West
- West Midlands
- Yorkshire and The Humber
Southern England and part of the Midlands will be hotter than Ibiza today, forecasters say.
"Lots of strong sunshine throughout the day. UV levels will be high and we'll see some very high levels of grass pollen," Met Office meteorologist Clare Nasir said.
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"Not a lot of change through the afternoon. A small chance of an isolated shower over the highlands of Scotland. But look at these temperatures coming in, at the very best I'd say 27C to 29C and pleasantly warm along the east coast."
Weather-health alerts differ from Met Office's weather warnings, with the latter used to highlight significant rainfall, snow, thunderstorms and winds typically.
Met Office works with UKHSA, a government department, to issue weather-health alerts when temperatures hit dangerous levels between June and September.
It has been in operation since 2004 and is designed to help healthcare professionals manage through periods of extreme temperature. Should conditions for an alert be reached outside of this period, an extraordinary heat-health alert will be issued and stakeholders are advised to take the usual public health actions
The current warnings remain in place until 9am on Monday morning.
