Just when you thought it as safe to breathe again in London, the city is planning for another spate of fog and smog as bad as it suffered back in the 1950’s.

“The Great Smog of London or Great Smog of 1952 was a severe air-pollution event that affected the British capital of London in early-December 1952. A period of cold weather, combined with an anticyclone and windless conditions, collected airborne pollutants – mostly arising from the use of coal – to form a thick layer of smog over the city. It lasted from Friday, 5 December to Tuesday, 9 December 1952 and then dispersed quickly when the weather changed.”

The big difference between the 1950’s smog and the smog of 2018 will be its source. While the source of the 1952 smog was fossil fuels that made the smog intolerable to breathing. The modern version will only be moderately polluted; a provide mainly lack of visibility rather than a danger to health.

The British Meteorological Office (Met) sent out a warning to states that “Isolated pockets of moderate air pollution are possible over central and western parts of the UK on Thursday, especially where light winds and foggy conditions allow the buildup of locally emitted pollution, such as near busy roads. Isolated pockets of pollution are again possible on Friday and Saturday.”

The Department for Environment, Food and Rural Affairs (DEFRA) stated that they predict moderate air pollution levels in some central regions tomorrow, Friday and into the weekend.

The cause was explained in lieu of the recent arctic cold front that hit the country, where clear skies will cause the ground temperature to drop quickly causing the air moisture to condense into the fog and thicken without winds to blow the fog away.

Since this fog warning is severed, all UK channels are broadcasting it, and statements are similar on all channels. Forecasters are saying “Mists will quickly develop tonight turning readily into the fog, mostly across western areas.” and “This fog will become more extensive overnight, and we are expecting frosts in the morning with temperatures expected to drop to below freezing.”

In most instances visibility will become limited to 100 meters, so drivers are warned only to go out if absolutely necessary. Flights will be delayed in some airports, and the temperature is forecasted to be around -2C (28.4F) to -3C (26.6F)