UPDATE at 3.00pm: 22 departures and four arrivals now cancelled at London City Airport

ORIGINAL STORY: The Met Office issued a yellow weather warning for the third consecutive day on Wednesday morning (25 January) as freezing fog again descended on the south-east of England, bringing chaos to roads and airports.

Dense fog continued to wreak havoc over London's runways, although early signs suggested that the effects would be less profound than during the previous 48 hours, when more than 200 departures from Heathrow were cancelled alone.

As of 9.30am GMT, 40 outbound flights from Heathrow airport had been cancelled and 150 were scheduled with delays. Typically, these numbers rise throughout the day.

At London City airport, seven flights had been cancelled and a further seven delayed by 9.30am. Services at London Luton airport appear to be running normally.

After another night of sub-zero temperatures, London awoke to a frosty morning with temperatures only rising above freezing at around 9am. Highs of 4C are expected in the afternoon followed by lows of -2C overnight.

Commenting on the third consecutive yellow – or 'be aware' – warning, the Met Office's chief forecaster said: "Travelling conditions will be difficult with journeys likely to take longer than usual and delays to air travel are possible. Stagnant air will remain across the area, allowing fog to form readily. Frost deposited by the fog will give surfaces an icy covering, which may be thick enough to make roads and pavements slippery."

The cold weather also contributed to London's first 'black' alert pollution warnings on Monday (23 January). The cold, stable atmosphere allowed pollution to escalate to dangerous levels, according to data recorded by the London Air Quality Network.

It is the first time that such extreme levels of pollution have been recorded since Mayor of London Sadiq Khan introduced the new air-pollution recording system in the summer of 2016. The mayor described the situation as "shameful".

IBTimes UK will be continue to bring the latest weather and travel updates.