
Britain was shrouded in a cloud of Saharan dust today as smog lingered over parts of the country while temperatures soared - making it the hottest day of the year so far.

The mercury has so far peaked at 21.2C in St James's Park, central London, this afternoon, where air pollution was at its highest levels after dirty air from the Continent mixed with the African dust cloud.

Health experts advised those with asthma and the elderly to stay indoors and avoid strenuous exercise while the air became more dense with pollutants.

A low pressure system arriving overnight should disperse the pollution but this will leave tomorrow feeling fresher and cooler with rain forecast over the weekend.

Scroll down for video

Hazy: A layer of smog clouds central London with the skyline of Canary Wharf barely visible in the background (to the right). Tower Bridge stands prominent in the foreground

Blurred: The Shard, one of London's most iconic buildings, is pictured shrouded in smog on Friday afternoon

Map: This NASA MODIS satellite image shows the build up of air pollution over south-eastern England on Thursday. The satellite is yet to pass over Europe yet today to uncover the level of pollution affecting the country on Friday

Murky: The panoramic views of the Lake District were barely visible today as a mix of Saharan dust and air pollution smother the UK today

Smog: Central London was shrouded in a layer of smog this morning as Defra issued a high level pollution warning for the capital

City skyline: The iconic views of central London are barely visible as the area is shrouded in thick smog and air pollution is at its highest rate

Clean me: As the Saharan dust cloud passes over the south east of England, cars are becoming covered in a film of red dirt, leading someone to write 'please wash me' on the rear windscreen of this car in Kent

Six regions recorded high pollution, including Eastern, South East, East Midlands, Greater London, West London, West Midlands and Yorkshire and Humberside areas, which were all affected by poor air quality.

The levels are so high because of a combination of the African dust cloud, which is due to fall tomorrow and leave a yellow or brown film on cars - a phenomenon dubbed 'blood rain', combined with dirty air from the Continent.

And today's fine weather is only said to help trap the toxic cocktail over the UK, with areas along the south coast including Eastbourne and Brighton said to be the worst affected.

Dr Steven Godby, a geographer researching the effects of blown sand and dust at Nottingham Trent University, explained how these events can occur.

Warning: Experts are advising those with breathing difficulties to take care in today's sunshine as air pollution levels will reach 'very high' in the South East

He said: 'Dust events like this are not uncommon in the UK and we witnessed one contribute to extremely poor air quality in parts of the country a year ago under similar synoptic conditions.

'The dust is produced from source areas in North Africa, incorporated into a northerly airflow and can travel long distances before being deposited as far away as the UK.

'However, the events we experience are small scale compared to those experienced closer to major dust sources.

'Just last week a major dust storm swept across the Arabian peninsula, affecting travel and air quality before passing over the Arabian Sea and causing a major pollution alert in Mumbai, India.'

Asthma sufferers, people with heart problems and older people are being advised to 'reduce physical exertion' particularly while outdoors.

At high concentrations particles can travel into the lungs and cause short term health effects such as irritation to eyes, nose, throat, sneezing, coughing and shortness of breath.

Dr Sotiris Vardoulakis, head of the air pollution and climate change group at Public Health England's Centre, said: 'While most people will not be affected by short term peaks in air pollution, some individuals, particularly those with existing heart or lung conditions, may experience increased symptoms.

The Department for Environment, Food and Rural Affairs (Defra) has warned air pollution could reach very high levels in areas of south east England, while eastern England is likely to see high levels (see map, right).

The London Air Quality Network, operated by King's College, has also forecast high particulate levels at busy roadside locations in the capital today, with poor dispersal of local emissions.

It also predicts light easterly winds will bring in air from industrial areas of northern France and Belgium.

Pollen is also causing issues for allergy sufferers, according to medics who have seen a rise in the number of patients experiencing symptoms.

While levels are moderate for much of the south of England and low for the rest of the UK according to the Met Office, many people are already suffering from hay-fever symptoms.

Andrew Williams, nurse consultant at Homerton Hospital, east London, told the Daily Express: 'People have already been coming in with symptoms triggered by the London plane trees.

'Now we are seeing high birch pollen levels, a lot of sufferers are presenting slightly earlier than usual as the problem gets worse.'

Quick dip: Warmer temperatures in Brighton, East Sussex, brought several people to the beach to make the most of the weather conditions

Getting comfy: Two ladies sit on stripey deckchairs on the pebbles of Brighton beach as temperatures reached 15C on the seafront today

Ride: People take a ride on the Volks Railway seafront tram at Brighton beach today where conditions remained warm and dry

Warm spells: One couple walking along Brighton beach enjoy an ice cream today after smog that covered the area lifted

Relax: Another pair take some time out to enjoy the south coast, where it remained warm and dry for the time of year this afternoon

Family time: A couple and their dog enjoy a spot of lunch at Broadway Tower in the Cotswolds today as a family explore the folly

Cooling off: A woman enjoys an ice cream in the sunny weather at St James's Park in central London this afternoon, where temperatures reached 21.2C - warmer than any other part of the country

Chilling out: A group of girls take some time out and lie on top of their luggage at St James's Park in London, which was shrouded in smog earlier today

Sunny: A pair of cyclists enjoy the unseasonal warm spell while they can as tomorrow is set to bring with it cooler and fresher conditions

Down time: A lady sensibly wears a visor to protect her eyes from the sun while she reads in St James's Park in London this afternoon

Strike a pose: Two girls use a selfie stick to take a picture in the sunshine at St James's Park today. Temperatures will drop to around 13C over the weekend

Lunch time: Teachers Sarah Harris-Watkins (left), from Ashby-de-la-Zouch, Leicestershire, and Katie Glover, from Sutton Coldfield, sat enjoying the sunshine and eating strawberries in Stratford-upon-Avon today

Picnics: Several people made their way to Primrose Hill in London today for some lunch while the city basked in some of the warmest temperatures

Cuddled-up: A couple look out over the views of London from Primrose Hill as sunny spells left the capital basking in higher than average conditions

Fresher, cleaner air from the Atlantic is expected to arrive tomorrow although pollution levels will remain moderate for many areas over the weekend, Defra said.

But the latest spike in dirty air has prompted renewed calls from environmental and health campaigners for more action to tackle the problem of air pollution, which leads to the premature deaths of tens of thousands of people a year.

Dr Penny Woods, chief executive of the British Lung Foundation, said the latest pollution episode was 'troubling', coming soon after the last such event, and could put people living with respiratory conditions at risk of worsening symptoms.

'To reduce the impact, people who find their health affected can take simple steps such as avoiding busy roads, especially during rush hour, and refraining from strenuous exercise outside,' she said.

'Those who use a reliever inhaler should always carry it with them and, if symptoms continue to intensify, contact their GP. That said, people living with lung conditions shouldn't have to take such steps simply to avoid being made ill by the air they breathe.

'With periods of high pollution often resulting from a combination of domestically-produced pollution and that coming from mainland Europe, we need urgent action from government to clean up the air we breathe, across all government departments at home and at a pan-European level.'

Friends of the Earth's South East campaigner, Brenda Pollack said: 'Air pollution kills tens of thousands of people prematurely in the UK every year, and puts extra pressure on our overstretched NHS.

'Ministers must protect our health by acting urgently on the main cause of air pollution, which is too much dirty traffic. Plans for new roads will make things worse.

'We need to see less traffic and more walking, cycling and public transport use. This will improve health and enable us all to breathe more easily.

'Action on air pollution will also help us to stop dangerous climate change - the UK should focus on this rather than giving its support to dirty oil and gas projects that threaten our climate and pollute our air.'

Foggy: Fresher, cleaner air from the Atlantic is expected to arrive tomorrow although pollution levels will remain moderate for many areas over the weekend

Campaigning: The latest spike in dirty air has prompted renewed calls from environmental and health campaigners for more action to tackle the problem of air pollution, which leads to the premature deaths of tens of thousands of people a year

Toxic: Today's fine weather was only said to help trap the toxic cocktail over the UK, with areas along the south coast including London, among the worst affected

Sweltering: Smog still hung over the capital even as temperatures sweltered to more than 21C at 2.50pm in central London today

Dense: Canary Wharf in central London was virtually non-existent for the first half of Friday morning as it as covered in a blanket of smog

Polluted: The worst affected areas stretched from London (pictured Stratford in east London) to the north east in Yorkshire and Humberside

Smokey: A chimney billows fumes into the already polluted skies over Ramsgate in Kent this morning, where conditions will clear by tomorrow

Misty start: People walk along the beach with their dogs in the early morning hours on Friday in Ramsgate in Kent as pollution levels peaked

Obscured: A family and their pets run along the beach at Ramsgate in Kent but the port in the background is barely visible due to thick smog

Blur: The sea blends with the sky as mist lingers over the port of Ramsgate in Kent this morning, where a ferry can be seen pulling away

Mysterious: The Lake District was shrouded in fog this morning as doctors also warned that levels of pollen had gone up today too

WHEN THE SAHARA'S DUST MET EUROPE'S DIRT Yesterday's smog was due to a combination of the calm weather and the arrival of extra dirty air from overseas. Mild conditions in the UK meant any normal pollution had not been blown away, and this was then mixed with more dirty air blown in from Europe. The smog was then worsened by a cloud of dust from the Sahara desert in North Africa, that was whipped into the air during a storm and carried more than 2,000 miles to Britain. Dr Steven Godby, a geographer at Nottingham Trent University, said: ‘Dust events like this are not uncommon in the UK and we witnessed one contribute to extremely poor air quality in parts of the country a year ago under similar conditions. ‘The dust is produced from source areas in North Africa, incorporated into a northerly airflow and can travel long distances before being deposited.’ People with existing lung and heart conditions can suffer unpleasant symptoms if they breathe in the fumes. At high concentrations particles can irritate the eyes, nose and throat, causing sneezing, coughing and shortness of breath. Advertisement

Met Office spokesman Dan Williams said the warmest temperature recorded today was 21.2C in St James's Park in central London at 2.50pm, but it could still peak yet.

He explained that areas in the sunshine were where the warmest temperatures were recorded.

'It's not record-breaking by any means, but it's pretty warm for this time of year - early April maximum average temperatures are around 11C to 12C, so to see 22C is well above average,' he said.

Mr Williams added that the very still weather, which has led to the high levels of air pollution, would be replaced by gradually breezier conditions as a weather front came in from the Atlantic this evening.

The warm weather would be replaced by fresher and cooler conditions over the weekend, with temperatures around 13C to 14C - much closer to the average for the time of year. Most places are likely to see a drop of 5C on current highs.

Mr Williams said: 'The front coming in from the west will effectively strip all of that pollution out of the way as it comes through. There will be a change of wind direction and become breezier, which will take all that pollution away.'

Met Office meteorologist Charles Powell added that by Saturday morning temperatures will be lower after a band of rain overnight.

He said: 'It's not that it's going to be particularly cold, it's just returning to nearer normal after a week of temperatures being above average, so it will feel slightly colder.'

Tomorrow will see cooler temperatures of around 10C or 11C in the North of England, where the Grand National will be held at Aintree, and about 14C or 15C in the south during the annual Boat Race on the River Thames, where it's likely to be the warmest part of the UK.

Sunday is also expected to be much cooler but with some dry, sunny spells. It will be welcome news for runners in the Brighton Marathon, which takes place in East Sussex on Sunday morning.

Mr Williams, from the Met Office, added: 'Brighton will see some dry, sunny spells with temperatures at around 14C on Sunday.'

Dawn: Colourful skies are seen over the Wiltshire town of Malmesbury as sheep graze in fields as the country gears up for sunny weather

Picturesque: The sun rise created beautiful reflections of the Duke of Portland boathouse on the shoreline of Ullswater in the Lake District

Dense: Parts of the country are covered by a layer of smog this morning as air pollution levels reach their highest in the South East, pictured the central London skyline shrouded in fog today

Skyline: Blue skies are visible through the remaining layer of mist in Birmingham where temperatures will reach around 17C today

Emissions: Much of the West Midlands, including Birmingham (pictured) is subject to high levels of pollution from dust particles today

Grey: Swindon in Wiltshire can be seen through the hazy light this morning as it was also affected by high levels of air pollution after a combination of dirty air from the Continent and dust particles from the Sahara sweep across the UK

Dirty air: Experts have advised those that suffer with asthma and the elderly to stay indoors and avoid strenuous exercise until the dust settles

Silhouettes: Parts of London were barely visible by the cloud of thick smog hanging over the city this morning. A low pressure system arriving overnight should disperse the pollution with tomorrow feeling fresher and cooler

Selfie: Visitors to the Shard's viewing platform pose for pictures with a backdrop of London, which has started to clear from the haze

Selfie: A young girl takes a picture of herself from the viewing platform at The Shard in south London as it was shrouded in smog today

Aerial: The view from the Shard building, overlooking the city, shows the fog has lifted but still remains looming on the skyline

Gloomy: The City of London, pictured from the Shard, was slightly hazy today on what is said to be the hottest day of the year so far

Bright: Today's fine weather is only said to help trap the toxic cocktail over the UK, pictured, the sun breaks through the mist in London

Mist: Britain is gearing up for what is set to be the hottest day of the years so far as the early morning mist clears in Rodley, West Yorkshire

Temperatures are set to soar to 22C in parts of the country today once the heavy fog lifts, pictured sunrise at Seaton Carew in Hartlepool today

Murky: A thick cloud of smog shrouded the River Thames this morning, where air pollution levels are at their highest. Pictured, the Duchess M and Thames Workboat Avante on the river

Fumes: Much of the UK woke up to hazy conditions (pictured, a horse grazing in Seaton Carew, Hartlepool) where pollutants have filled the air

Murk: Much of the backdrop of the Lake District is barely visible behind the layer of smog as it hangs over Ullswater on Friday morning

Rowing: Oxford University's Isis crew turn under Putney Bridge during training ahead of the Boat Race on the River Thames this morning

Training: The Oxford University women's rowing crew are unfazed by the smog as they practice on the River Thames ahead of tomorrow's race

Murky conditions swathed Seaton Carew this morning where visibility was poor. But the fog is expected to burn off in today's warm sunshine

Burning through: The sun peeks through thick clouds in the village of Rodley near Leeds this morning, where it will be about 19C later on

A combination of dirty air from the Continent and a Saharan dust cloud have caused air pollution levels to reach their maximum in some parts of the country. Pictured, horses grazing in Rodley, West Yorkshire

Hues: The sun rises behind the Wallace Monument in Stirling creating a spectacular range of reds and purples colours in across the sky

Comparison: Aoife McClearly shared her view from Unilver House in Blackfriars, central London, this morning (left) compared with how it usually looks on a clear day (right)

Sunrise: The sun comes up over Hastings in East Sussex this morning, one of the areas affected by the high levels of pollution, but also expected to be among one of the warmest parts today

Daybreak: Bournemouth (left) is expected to reach around 14C today, on what is expected to be the hottest day of the year so far, while Gravesend in Kent (right) will be slightly warmer at 17C

Hazy: The sun comes up over Bournemouth Pier this morning, which is expected to be packed with beachgoers hoping to catch some rays

Stunning: A walker makes the most of the warmer weather in the Lake District as the perfect still of Derwentwater and reflects its surroundings

Mirror image: The Crummock Water in the Lake District looks idyllic as it shapes to be one of the hottest days of the year so far

Crystal: A mallard glides across the glass-like waters of Ullswater on Friday morning ahead of a day of warmer temperatures across the region

Eerie: 'Spaceship-shaped' clouds were spotted above Ullapool on the west coast of Scotland on Thursday evening by Neil Borthwick

Unidentified flying object? The 54-year-old snapped these pictures above Loch Broom of the rare lenticular clouds, which are created in certain conditions when air is pushed upwards by a mountain. They are one of the most common causes of UFO reports but tend to be rare in the UK

Basking: A group of seals laze about in the sunshine at Newburgh beach in Aberdeenshire this afternoon as parts of the country enjoy the sun