UK swelters on another hottest day
Image copyright PAA health warning for heatwave conditions is in place for parts of the UK until Thursday evening.
The yellow warning means there is an 80% chance of temperatures being a risk to health.
Tuesday is officially the hottest day of the year so far - with 30.6C, recorded in Porthmadog, Gwynedd, beating Monday's peak.
The hot weather is expected to last until the weekend, when temperatures are forecast to slowly drop off.
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The Met Office issued the yellow health warning for the west and north-east of England, in place from 09:00 BST on Tuesday until 18:00 BST on Thursday.
It is intended to help social and healthcare teams prepare for the potential dangers a heatwave can present, especially to the very young, the elderly or those with chronic disease.
There's also bad news for hay-fever sufferers as very high levels of pollen are forecast across England, Wales and Northern Ireland throughout the week.
Some schools have said they are cancelling sports days because of the "extreme heat".
Hottest day... so far
Temperatures on Tuesday crept higher than the maximum of 30.1C registered in west London on Monday.
In England, the hottest spot was Rostherne, Cheshire, with a temperature of 30.3. Aviemore recorded Scotland's peak, with 26C, while Castlederg in County Tyrone was Northern Ireland's high point, with 27C.
The Met Office says the UK could reach 33C on Thursday.
Media playback is unsupported on your deviceBBC Weather presenter Ben Rich said Wednesday could start out "cloudy and murky" on the east coast of Scotland and eastern England but that the skies would clear over the course of the morning.
He said: "Then it is another plain sailing day, with long spells of hot sunshine, and by this stage even Northern Ireland and Scotland will be close to 30C."
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The heat will continue until the weekend, with cooler weather in eastern areas and the chance of a shower on Sunday, he said.
- How are you handling the UK heatwave? You can share your experience by emailing haveyoursay@bbc.co.uk. Or fill out the form at the end of the page.
The heatwave has been attributed to the jet stream looping to the north of the UK, and then back down to eastern Europe, creating an area of high pressure over the country which is not shifting.
However, for Greece, the direction of the jet stream has produced very stormy conditions.
Heatwave health warnings explained
Green - minimum state of vigilance during the summer.
Yellow - Alert and readiness - Social and healthcare services are on standby to reduce harm.
Amber - Heatwave action - Care services target high-risk groups, like the elderly, with specific help. General advice is given to keep homes cool, drink plenty of fluids, and so on.
Red - National emergency - Reached when a heatwave is so severe that illness and death may occur among the fit and healthy, not just among high-risk groups.
Threshold temperatures for triggering these warnings range from 28C in north-east England to 32C in London.
Fears that railway tracks could buckle in the heat prompted Network Rail to introduce speed restrictions.
The railway infrastructure operator said track temperatures could reach as much as 20C above the air temperature, meaning the steel rails can expand markedly. The reduced speeds are intended to lower the force exerted on the track, reducing the risk of buckling.
Meanwhile, police have urged people to be careful of the temptation to swim in open water in the hot weather.
The warning came after the body of a man was recovered from a lake in Nutfield, Surrey, on Monday.
A search is continuing for a missing 13-year-old, named as Ryan Evans, at Westport Lake in Stoke-on-Trent.
The heat also started a wildfire across two square kilometres of moorland in Greater Manchester.
And in York, police officers smashed the windows of two cars to rescue dogs "struggling to breathe" inside. Police said they had referred the car owners to the RSPCA for prosecution.
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