BRITONS are set to bask in a three-day sunny and hot spell before it all goes wrong at the weekend.

The week is getting off to a warm start with most of the UK forecast to enjoy some summer sun and we should enjoy temperatures in the low to mid-20s.

A wave of hot air - known as a Spanish plume - was expected to sweep across the UK from Spain but a change in direction means the predicted highs of 30C (86F) and above are unlikely, the Met Office said.

The air, now expected from the south-east rather than the south, will be less humid, meteorologist Alex Burkill said.

He said: "It will still be above average for the time of year. It will definitely feel like summer, perhaps just not as hot as we thought it would be."

Temperatures will fall short of mid July's record this year of 33.5C (92F).

Warning sunseekers to be careful when out and about in hot weather, St John Ambulance advised people to keep in the shade where possible, stay hydrated and wear sun cream.

Training officer Clive James said: "The classic signs of heat exhaustion and heat stroke are dizziness and headache - if you're suffering from either, find somewhere cool and drink plenty of fluids. If your symptoms don't get any better and you're concerned, seek medical attention."

Mr Burkill reassured those concerned about problems trying to sleep through muggy nights.

He said: "It is likely to be quite chilly overnight, with temperatures falling to single figures in some places. It could be around 3C or 4C (39F) in parts of Scotland."

The good weather is not expected to last long as unsettled conditions are in-store for Thursday and into the weekend.

The highs of around 24 in Sussex for today and tomorrow are expected to go down to about 19 by the time we get to Friday.