Many parts of Britain enjoyed more warm weather today as temperatures continued at up to 10C above average for the time of year.
The Met Office said it was the fourth mildest start to December across the UK since 1960.
The temperature at London City Airport reached 16C - above the average for May in central England of 11.2C and far higher than the December average of 6C to 8C for the UK.
The weather has been so mild that daffodils have been flowering as far north as Chester and Northern Ireland.
A band of tropical air coming off the Atlantic from the south west is behind the unseasonal weather, and temperatures are edging towards the all-time December high of 18.3C, set on December 2 in 1948 in Highland, Scotland.
A Saharan dust cloud is expected to settle over parts of the UK tomorrow, prompting health experts to issue warnings to the elderly and those who suffer from breathing problems.
High levels of pollution are expected over southern and central England, with Lincolnshire bearing the brunt of the cloud.
Gemma Plumb, a forecaster with MeteoGroup, said there were many readings of 15C today across southern and eastern parts of the UK.
The 16C reading at London City Airport was between 1pm and 2pm.
The Met Office said that looking at figures dating back to 1960 this had been the mildest start to December for Wales (8.7C), south-west England (9.8C) and south-east England (10C), and the fourth warmest for the UK as a whole (7.1C), with 1979, 2000 and 2006 being marginally milder.
Early provisional figures showed the first half of December had been very mild across England and Wales. However there had been a sharp north-south contrast at times with much colder air over Scotland and some frosts.
Despite the mild start to winter following on from a mild autumn, it looked like 2015 would be an average year.
A spokesman said: "This year's damp and cool spring and summer mean that despite the current mild spell, the rainfall, temperature and sunshine statistics for the year as a whole are all hovering around average."
The warm weather has brought about some bizarre sights in gardens and parks, including daffodils blooming, despite their usual season for flowering being between February and May.
Wirral Bird Club posted on Twitter a photograph of daffodils flowering in Chester, saying: "The weather has gone mad. Daffodils in flower in mid-December in Chester," while another user showed a picture of daffodils in full bloom in Downpatrick, Northern Ireland.
Another Twitter user, under the name @diamondgeezer, posted a photograph of a field of daffodils in London's Olympic Park, saying simply: "#climatechange".
Not even the recent flooding in Cumbria could drown out the daffodils, with Kendal Gardening tweeting: "After floods have come the Daffodils! In the Lyth Valley in mid December! Madness!"
The Department for Environment, Food and Rural Affairs (Defra) issued alerts over Saharan dust for most of England and Wales, warning that the elderly, asthma sufferers and those with breathing difficulties were most at risk. People were advised to avoid exercise if they noticed problems.
Defra said: "Adults and children with lung problems, and adults with heart problems, should reduce strenuous physical exertion, particularly outdoors, and particularly if they experience symptoms.
"People with asthma may find they need to use their reliever inhaler more often. Older people should also reduce physical exertion."
Asthma UK warned of a "perfect storm" of conditions to cause problems for asthma sufferers, with temperatures hovering around 17C.
Andrew Proctor, director of advice and support, said: "People with asthma need to take extra care. We are facing a perfect storm of asthma triggers, with air pollution and weather changes increasing the risk of potentially fatal asthma attacks for millions of people with the condition.
"Two-thirds of people with asthma find that air pollution makes their asthma worse, and even more tell us that changes in the winter weather can trigger asthma attacks.
"If air pollution or cold weather makes your asthma worse, do check forecasts and carry your reliever inhaler with you at all times."
The Met Office said the mild southerly airflow currently affecting the UK brought an increased chance of seeing some of the dust, which had been lifted from its source in west Africa by strong winds and was being blown northwards as it was caught up in weather systems heading towards the UK.
The dust is lifted by strong winds and can reach very high altitudes. From there, it can be transported worldwide by winds, covering distances of thousands of kilometres.
The dust gets caught in rain droplets in clouds, falling to the ground in rain. When the water evaporates, a thin layer of dust is left on surfaces, such as cars.