With the mercury expected to hit 30C (86F) and more today, Public Health England (PHE) has warned the most vulnerable, including older people, young children and babies, could be at risk.
But while East Anglia could see temperatures of 30C - and as high as 32C in London - the Met Office said this morning maximum temperatures in Yorkshire would be a less oppressive 24C (75F).
Met Office meteorologist, Helen Roberts said: “(In Yorkshire) we are looking at patchy cloud but some decent spells of warm sunshine.
“We have a weak cold front straddling the UK and Yorkshire is just on the colder side of that.
“All the heat is focussed across the South East corner of the country to the warm side of that front.”
She added: “It depends on where you are, and your perspective, but most people would think it was a pretty pleasant, warm summer’s day, not particularly oppressive because you don’t have the humidity of the South East which makes things more hot and sticky.”
Alerts have been issued covering the East and South East.
Temperatures hit 29.7C (85.5F) in St James Park and 30C in Gravesend, Kent yesterday.
The heat has prompted PHE to urge people to take extra care during the hot days and warm nights.
Public health medicine consultant, Dr Thom Waite said: “Now the heatwave has arrived, people will likely be out and about more enjoying the summer sun.
“That’s why it’s really important to remember that there are some people whose health suffers in hot weather.
“Older people, those with underlying health conditions and young children may all feel the ill-effects of heat over the coming days.
“We’re urging everyone to keep an eye on those you know who may be at-risk this summer. If you’re able, ask if your friends, family or neighbours need any help.”
Dr Waite said the hot weather can “put extra strain on bodies” and urged people to “stay hydrated” during the hot spell.
Top PHE tips to keep cool include closing curtains, keeping out of the sun between 11am to 3pm, wearing loose fitting cotton clothes and applying suncream.
As well as looking out for others during the heatwave, the body advised to not leave anyone or animals in a closed, parked vehicle.
Met Office forecast for Yorkshire...
Any early mist will soon clear, then a dry day with bright or sunny spells. Cloud may thicken later to give a risk of some evening rain, possibly thundery. Winds light and with onshore breezes developing coasts will be cooler. Maximum Temperature 24 °C.
Rain may affect some areas for a time, but it should be a dry end to the night for much of the region, with winds remaining light. Minimum Temperature 15 °C.
Outbreaks of showery rain are likely to become more persistent and heavier with the risk of thunder. Winds light northeasterly. Maximum Temperature 19 °C.
Outlook for Friday to Sunday:
Friday looks dry with sunny spells. Some cloud and rain is likely on Saturday, mainly in the morning, with afternoon sunshine likely. Sunshine and showers on Sunday.