Britain's third heatwave of the year is expected to hit its "absolute peak" today as temperatures climb into the thirties with wildfire alerts issued.
After the UK witnessed temperatures of 34C on Monday, mercury is today expected to reach highs of 36C in London.
Weather experts said today will see the start of the "absolute peak" heat, although humidity levels are expected to be lower than during the late June heatwave.
A Met Office spokesman said: "The highest temperatures of the current spell are expected on Thursday and Friday, when temperatures will widely exceed 30C across England and Wales, with highs of 35C on Thursday and potentially 36C in some locations on Friday.
According to Met Office forecast, temperatures in the high twenties will remain consistent throughout today across the South East of England, South West of England and North of England.
Areas of Scotland and South Wales should expect slightly cooler temperatures in the low twenties, while London and the Midlands will roast in 32C to 34C heat later today.
Fire chiefs have flagged the increasing risk of wildfires likely with dry and hot weather, advising people to avoid using disposable barbecues in open countryside and park.
Meanwhile, a number of train services are impacted by the extreme weather, with c2c, Greater Western Railway and London Northwestern Railway among operators disrupted.
Temperatures are expected to hit at least 34C in London today, with a chance of peaking at 36C
|MET OFFICE
Daily peak temperatures are expected to remain above the 28C threshold for an official heatwave through to early next week, then seeing a drop, with 27C forecast for Tuesday, before rising back up to 29C on Wednesday.
The expected nine-day heatwave comes after two periods of extreme weather in June, which amassed the highest June temperatures on record, pushing close to 40C heat.
Amber and yellow heat health alerts have been issued by the UK Health Security Agency, meaning significant impacts are likely across health and social care services due to the high temperatures.
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Tom Crabtree, deputy chief forecaster at the Met Office, said: “High pressure is expected to remain in charge through much of next week, but it will gradually migrate northwards.
"This means that an easterly wind will become established in the south, and the focus for the hottest conditions will migrate towards the southwest.
“As a result, some places that have seen the highest temperatures during recent weeks will begin to cool. It will however, remain very warm - especially in the southwest - and heatwave thresholds may continue to be met in places.
“The overall signal is for continued fine, dry and very warm weather at times for many parts of the UK into next week. There is however a chance of thunderstorms spreading into parts of the south and southwest.”
A National Fire Chiefs Council spokesman stressed it can only take one spark to start a wildfire in these temperatures, and what can begin as a small fire can spread fast – "putting people, homes, wildlife and our countryside at risk".
"We’re asking everyone to take extra care outdoors, whether that’s avoiding disposable barbecues in the countryside, parks or moorlands, or making sure cigarettes are fully extinguished," the spokesman added.
Meanwhile, Ross Macleod, RNLI water safety manager, equally warned the sea remains cold enough year-round to trigger cold water shock, which can cause "uncontrollable gasping, increased heart rate, and can lead to panic and drowning very quickly".
“It’s best to enter the water slowly to gradually acclimatise," he added.
"Anyone who finds themselves in danger in the water should fight the panic instinct and float to live - try to relax and float on their back, with head tilted back, gently moving their hands and legs to help them stay afloat."
NHS England has also said many of its ambulance services will be under "sustained pressure" due to the extreme heat this week.
Professor Frankie Swords, NHS national medical director, said people, especially children, the elderly and those with existing health conditions, should "take the weather seriously", while others should also look out for anyone who may be vulnerable.
She added: “The extreme heat means that many of our ambulance services are under sustained pressure, but as always, patients should always call 999 in a life-threatening emergency or 111 if less urgent."