Londoners are set to bask in glorious sunshine and enjoy the warmest April day in nearly 70 years, forecasters predict - but people are being warned to stay indoors due to 'toxic' pollution enshrouding the capital.
Temperatures could soar to as high as 28°C on Thursday (April 19) becoming hotter than Portugal and Ibiza while far surpassing the average maximum temperature for this time of year, which stands at 11.4°C.
The dry, very warm and sunny weather is set to stay put from Thursday right through until Saturday (April 21), The Met Office has said.
But it's not all good news, according to The Mirror , with experts warning Brits to be wary of enjoying the hot temperatures, with a toxic plume of pollution likely to cause problems for people with heart and lung problems.
The toxic air will happen because air from the Atlantic is mixing with polluted air in Spain and France.
Advice from the Department for Environment, Food and Rural Affairs (DEFRA) says: "Thursday and Friday have the chance of localised high pollution levels near east coasts of England, with isolated pockets also possible in busy urban areas in southern and eastern England.
"Areas of moderate air pollution are expected across southern parts of the UK, with more isolated moderate levels in the North, mainly close to coasts."
The summery spell comes as a result of warm air from the Azores, off the coast of Portugal, being dragged up towards the UK by the combined efforts of an area of low pressure over the Atlantic and high pressure over western Europe.
A high of 28°C would beat the 2001 April high of 27.8°C, the Met Office said.
The warmest April day on record was 29.4°C in 1949.
Meteorologist Alex Burkill said: "There's a fairly good chance of 28°C, there's about a 60% chance.
"Quite widely we are going to see low 20s, and for many it will be a little warmer than Wednesday."
A high of 25.3°C was recorded in St James' Park in London on Wednesday (April 18), making it the hottest day of the year so far.
Thursday is expected to be the hottest day of the warm spell, with weekend temperatures dipping slightly before showery outbreaks on Sunday (April 2).
Competitors in the London Marathon can expect hot and humid conditions with a forecast of between 21°C and 23°C, Mr Burkill said.
"There could be a shower but it's not very likely. It's not great conditions for running. In fact if any showers do come they might be very welcome," he said.
Some hayfever sufferers could be affected by high pollen counts, he added.
Mr Burkill said: "For anyone who suffers from tree pollen they will probably be feeling the effects, but that's only about 20% of hayfever sufferers. Grass pollen season comes later in summer."
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