Supercharged jet-stream winds north of the UK sandwiched between low-pressure storm systems to the east and west will drive the phenomenon, according to weather experts. The so-called omega block, which meteorologists say is unusual in its intensity, could push the mercury close to the 30C (86F)-mark in some parts this week. The highest temperatures will hit Scotland, northern and western Britain as warm southerly air sweeps northward around the tip of Britain.
Blue skies and sunshine will cause temperatures to rocket through the coming days before wind and rain eventually push in by the weekend.
Temperatures will hit 24C (75.2F) by the middle of the week, according to the Met Office, although some weather charts show thermometers nudging 29C (84.2F).
Met Office meteorologist Marco Petagna said: “High pressure is dominating the weather, this is a pretty intense high and it is quite unusual.
“This high extends unusually high right to the top of the atmosphere and is exceptionally well-developed, in terms of how it will affect the weather, over the next three days it is going to be largely sunny with rising temperatures.
UK weather forecast: Temperatures are set to hit close to 30C by the end of the week
“The jet stream is well away to the west and north taking unsettled weather systems away from us, this is allowing the high to become more established.”
Thermometers will hover in double figures even over the tops of hills thanks to the bizarre atmospheric set up, he said.
Blue skies and warm sunshine will hold out through much of the week before things turn more unsettled at the weekend, he added.
He said: “Because we have this high sitting over us, air is sinking and warming as it does so, we are looking at a lot of fine weather.
“Temperatures will probably peak on Wednesday with highs of around 24C (75.2F) although it will be largely another decent day on Thursday.
“This is pretty unusual, the average air pressure is around 1, 013 millibars with the average high around 1, 030 millibars, however this very intense high is showing values of 1, 1042 millibars.
“Low pressure to the west of the UK and another to the east with the high in the middle is something we refer to as an omega block.
“Later on Thursday, and from Friday into the weekend we will see a change with things turning a bit more unsettled.
“Next week it should turn nice again and this is the pattern looking further ahead.”
Hardly any inland winds will lead to poor air quality sparking warnings for people with breathing conditions to take extra care.
Defra (Department for Environment, Food and Rural Affairs) predicts moderate pollution levels across parts of the UK.
A spokesman said: “With light winds and warm temperatures locally, pockets of Moderate pollution are expected to develop, mainly across England and Wales.
UK weather forecast: Temperatures in Britain will nudging 29C
“Areas of Moderate air pollution are expected to become more widespread across the UK on Tuesday.”
Pollen levels are also expected to rise before the weekend with the Met Office predicting high counts across the whole of England by Thursday.
While Scotland and western Britain will enjoy the highest temperatures this week it may feel cooler further south, according to some forecasters.
And Britons hoping to crack out the suncream and barbecues this weekend may have to rethink their plans.
John Hammond, meteorologist for online weather service Weathertrending, said: “We seem to have got the spring back for the next few days and we are going to see more of this scintillating sunshine.
“Temperatures will be getting up into the mid to high teens in a few places and up to the low 20Cs in one or two places.
UK weather forecast: Jet stream showing classic Omega block pattern
UK weather forecast: Huge high over the UK bringing warmer air to the north and west
“Further south and east across England and Wales will never reach these dizzy heights, we are going to start to drag some cooler air in from the east as we go toward the middle of the week.
“It will still be pleasant in the sunshine, in the daytime with a lot of sunshine it is going to feel very nice indeed.”
Warmer weather could become a more permanent fixture in the run up to summer with some long-range experts predicting a June heatwave.
Early forecasts show the mercury rising steadily through the next six weeks with blistering sunshine on the cards for summer’s kick-off.
Exacta Weather forecaster James Madden said: “Temperatures could turn very warm for the time of year in parts of the country through the second half of this month.
“From the middle of May onwards temperatures could lift into the high 20Cs at the very least.
“High pressure is expected to dominate the weather through this period and as we go into the start of summer there is the potential for further warm weather.
“On current indications there is a chance we could be looking at a very warm start to summer and a flaming June.”
The Met Office’s Marco Petagna said high pressure will lead to a ‘temperature inversion’ as air aloft is forced to the ground, compressing and warming during the process.
“We could see unusually high temperatures over the tops of the hills and mountains, temperatures here could reach double figures,” he said.
“This is caused when high pressure causes air to descend and compress, warming as it does so, the air closer to the ground is cooler leading to a so-called temperature inversion.
“Usually we expect to see temperatures fall higher in the atmosphere.”
A Met Office spokesman added: “In an anticyclone (high pressure) the winds tend to be light and blow in a clockwise direction in the northern hemisphere.
“Also the air is descending, which reduces the formation of cloud and leads to light winds and settled weather conditions.”