The Met Office has issued an amber heatwave alert and urged people to avoid the sun as Britain's heatwave shows no signs of abating and continuing into August.
The country is now on a level three warning from the Met Office - one step below the most severe, at which point it is expected fit and healthy people will begin to experience health issues.
Britain is braced for what could be the hottest day of the year this week with temperatures forecast to reach 35C as the scorching conditions creep even higher.
This would beat this year's record of 33C reached at Porthmadog in North Wales on June 28.
Britain's hottest ever day on record is 38.5 degrees recorded at Faversham, in Kent, in August 2003.
London, Kent and East Anglia will feel the burn most severely, with a peak in temperature predicted for Wednesday and Thursday.
The northwestern regions will feel fresher, with temperatures in the low to mid 20s.
Scotland could experience highs of up to 25C, Wales could jump to 26C and Northern Ireland to 24C.
Government agencies are urging people to stay safe in the sun. A sunburn warning was issued by Public Health England after 220 people were treated in hospital for overexposure over the past two months.
It asked for “common sense” in the continuing heat, advising people to wear sun cream and clothing that covers the skin, and to limit the amount of time spent in the sun each day.
In its official guidance, the Met Office said people should "stay out the sun" until Friday.
Fire services across the country have told the public to keep mirrors and glass objects away from direct sunlight the items may reflect or magnify the sun’s rays on to flammable items such as curtains, causing them to burst into flames.
How to stay cool
- Stay out of the sun: If you do need to go outdoors, try to avoid the sun between 11am and 3pm, and don’t forget the sunscreen and plenty of water!
- Loose clothing: This isn't rocket science but wear loose cotton clothes in light colours. Cotton is lightweigh, breathable and also absorbs sweat - synthetic fibres trap heat. Light colours too reflect the sun's radiation.
- Keep your home as cool as possible: rather than throwing all your windows open during the heat, it’s often better to shade windows and shut them during the day. You can open them when it’s cooler at night and in the evening.
- Keep drinking fluids: while it’s tempting to reach for your usual cup of tea, a nice cold beer or glass of wine, if things get really hot it’s advisable to stick to water and diluted fruit juice. Sugary, alcoholic and caffeinated drinks can make you more dehydrated.
- Keep an eye on elderly friends and neighbours: People with friends, relatives and neighbours who may be less able to look after themselves should check up on them to make sure they’re alright
- Babies: less than six months old should be kept out of direct sunlight. Use a parasol or sunshade on their pram if you do have to go out. You should also make sure your child is wearing a hat big enough to protect their head and neck from the sun.
- Older children: older children may get sick of too much water, so try a mixture of diluted fruit juice, ice cubes and homemade fruit juice lollies to help keep them hydrated.
- Stop children overheating: Paddling pools, cool baths and minimal nightwear and bedclothes will all help keep your child from overheating.
- Cooling yourself down: Carry around an ice pack or, if you don't have one, a frozen drink. It might not be practical - it'll drip as it melts - but it's guaranteed to instantly cool you down. You can also run your wrists under cold water - that'll help to cool the blood.
- Swimming: It can be very tempting to go for a swim in a local lake or river to cool down during a heatwave but please remember to beware of the dangers of drowning during what could seem like a casual dip. A particular risk factor can be cold water shock, which is one of the biggest causes of drowning – temperatures in seas, rivers, canals and lakes can be a low as 15C in summer, around half that of swimming pools. The LGA (Local Government Association) says people should only swim in water “that is clearly marked as safe and under the control of a lifeguard”.
