Heatwave warnings extended to north-west England
The heatwave warning for north-west England has been raised to "level three" by the Met Office.
Western England and Wales were the hottest part parts of the country on Friday, with the east marginally cooler.
Level three warnings are in place for the South West and the West Midlands, but warnings for south-east England and London have been reduced to level two.
It was the hottest day of the year in Scotland, Wales and Northern Ireland.
Temperatures reached 29C (84.2F) at Prestwick, South Ayrshire, 31C (87.8F) at Porthmadog, north Wales, and 30C (86F) at Castlederg, Co Tyrone.
Heatwave warnings alert healthcare services to help those in high-risk groups such as the elderly and young children.
Meanwhile, HM Coastguard has issued safety advice to swimmers and sailors after call-outs in the past month were up by nearly a quarter compared with the same period last year - as more people take to the coast to enjoy the sunshine.
From 15 June to 18 July this year, it dealt with 2,859 incidents, up 668 - or 23% - on the same dates in 2012.
Chief coastguard Peter Dymond said: "If you are heading out for a swim, check the sea conditions and remember that even though the sea may look calm on the surface, there is the danger of strong currents underneath."
And he urged those taking to boats, canoes and kayaks to wear lifejackets or buoyancy aids.
The NHS in England said it was closely monitoring the performance of A&E departments as the hot weather continued, with casualty departments "very busy".
A spokesman said A&E had seen near record numbers of patients but it was not possible to tell at this stage how much of this was directly related to the hot weather.
In other developments:
- Firefighters tackled a grass fire covering an area of 200m by 200m at the southern edge of Epping Forest, east London
- A woman died after being pulled from the sea at Ingoldmells, near Skegness
- A calf that got stuck in mud as it tried to cool off by the River Hamble in Lower Swanwick, Hampshire, was freed by firefighters
- School teachers renewed calls for statutory maximum temperatures in which they can carry on teaching, as the heat continues to soar in classrooms
- Walkers and climbers in Scotland were warned to guard against potentially fatal dehydration, heatstroke and heat exhaustion as temperatures soar
- A 15-year-old boy died after falling into the River Roe near Limavady in County Londonderry. Politicians urged people to be on their guard in "soaring temperatures"
- In Hampshire, gritting lorries were out on the roads spreading a mixture of stone chips and dust to deal with melting road surfaces
- The Highways Agency said it would not have gritters on standby for major routes in the South East. It said it was confident road surfaces could deal with the heat
- A mountain fire of dry grass and bracken at Wattsville, Caerphilly, was put out
Level three alerts are triggered when threshold temperatures have been reached for one day and the following night, and the forecast for the next day has a greater than 90% confidence level that the day threshold temperature will again be met.
The threshold temperature for north-west England is 30C.
Eastern areas will see cooler conditions on Friday, with London and south-east England reduced to a level two warning, and the East of England reduced to a level one warning - the minimum state of vigilance.
Level two warnings are also currently in place for the East Midlands and Yorkshire and the Humber. These alerts are triggered by a 60% or higher chance of the threshold temperature again being reached on the second day.
North-east England remains on a level one warning.
Scotland, Wales and Northern Ireland are not included in the alert system.
The Met Office said it would become less hot for a time over the weekend, but temperatures are expected to increase again early next week with a likelihood of level three being reached again in some areas.
It is the UK's first prolonged heatwave since 2006, with six consecutive days of temperatures above 30C.
Research by the London School of Hygiene and Tropical Medicine has estimated there might have been between 540 and 760 extra deaths in England and 60 to 100 in Wales due to the hot weather.
Wednesday was the hottest day of the year, with 32.2C (89.9F) recorded at Hampton in south-west London.