Original article (in Croatian) was published on 1/14/2025; Author: Ivan Nekić
During the winter season, fog is a completely normal occurrence, not a “mysterious weather event that smells like chemicals and makes people sick”.
Since the beginning of the new year, social media has been flooded with posts about a “mysterious dense fog” that has covered the entire world, appearing at the end of 2024. It is claimed that the fog contains “dangerous chemicals” and causes various health issues, from respiratory problems to insomnia, has an unpleasant odor, and that particles “strangely sparkle” in videos. Several Facebook pages, as well as numerous private profiles, have shared this news.
The page Zivcana Zirafa shared a video (archived here) warning that this is not a usual weather event, but that the fog contains a “toxic cocktail of chemicals”:
“Mysterious fog in the USA and Europe. Cities across the USA and Europe, many of which rarely experience fog, are now covered with a dense, eerie fog that doesn’t dissipate, even during the day.
And while the media try to dismiss it as mere coincidence, let’s be clear – this is not an ordinary weather event.
This fog full of particles not only obscures the view but also smells like chemicals and makes people sick”.

The video has been viewed almost three thousand times, has six comments, and over 100 reactions.
The page “Slobodni od rodenja” shared a link to an article (archived here) published on the web portal “Nulta tacka” (archived here) titled “Mysterious Fog: The ‘Fogvid-24’ Phenomenon worries people worldwide”, also adding the following:
“The fog is not mysterious but intentional. They have technology with which they can poison us. In the near future, we will see what symptoms people will have after it. I hope I’m wrong, but…”

The article, published on December 31, 2024, presents “testimonies” from TikTok about health problems people are facing due to the fog and concludes that “the Fogvid-24 phenomenon encourages discussion about the potential impact of the environment on human health and raises questions that science has yet to explore”. Their post was shared by 54 users, and has 44 comments, and 82 reactions.
It’s important to note that there is no evidence to support claims that the fog observed in early 2025 was anything other than ordinary fog. Experts indicate that fog is a common occurrence during winter months and does not inherently contain harmful chemicals.
The page “Istina istina” shared a video about dense fog causing flight cancellations, adding the following (archived here):
“Mysterious fog is spreading around the world – Have you felt something STRANGE? This fog causes: drowsiness, fatigue, difficulty breathing, sneezing, coughing, depression, itching, and a salty sensation in the eyes; it induces nervousness and headaches!”

The post received reactions from 46 users, garnered eight comments, and the video was viewed over 1,400 times.
The post about the mysterious fog has also appeared on numerous private profiles. In this example, it’s clear that private reach is significant – the post has 157 reactions, 57 comments, and 38 shares. The post also states:
“Fogvid24 – Dense fog has covered large parts of the United States, the United Kingdom, and Europe, making travel difficult and causing health problems. Named ‘Fogvid24,’ the event allegedly caused cold and flu symptoms for hundreds of people exposed to the fog. What are we breathing in? Video and more information in the comments below”.
Through Google search, limited to the past month, we found that this news was spread in our region by web portals such as Alo!, Republika.rs, and the mentioned Nulta tacka. Foreign media, such as Daily Mail, New York Post, and Express U.S. also covered the story, but focused mainly on the citizens’ concerns on social media without providing context to the entire story, scientific explanations, weather forecasts, or air quality updates and health warnings, if issued.
The story about the “mysterious fog” spread across other social media platforms as well (1, 2, 3, 4, 5).
Fog caused flight delays
This phenomenon that spread across all social media was addressed by fact-checking websites Lead Stories and Snopes.
It is true that at various locations around the world at the end of 2024, dense fog was recorded, but there is no evidence that it was anything other than a natural phenomenon. On December 29, BBC reported that flights across the UK were delayed for the third consecutive day due to dense fog reducing visibility. Euronews published that due to fog, delays occurred in air traffic in the Netherlands and Poland, and Forbes provided an overview of flight disruptions in the US. Dense fog and strong winds were the reasons for flight delays in Texas, Arkansas, and Louisiana. The National Weather Service issued a warning for drivers due to dense fog in 12 U.S. states.
Typical winter phenomenon
The websites of the US National Weather Service feature information about fog and safety, which describe various types of fog and the conditions in the sky and on the ground that cause its formation. One type, radiation fog, is common especially in autumn and winter.
“Radiation fog is a very common type of fog seen throughout the United States. It usually lingers during autumn and winter. It forms at night when the air near the ground cools and stabilizes. When the air cools to its dew point, fog forms. Fog initially appears close to the ground and becomes denser as the air cools. Additionally, with cooling air at higher levels, it begins to rise, and it is particularly favored by calm weather and locations near water”, explain US meteorologists.
Lead Stories contacted the Canadian Weather Service for a comment, and they responded via email on January 3: “Fog forms naturally when water vapor condenses on the ground. Some types of fog, such as when warm, moist air flows over a cold surface in winter, do not dissipate during the day. Environment Canada has not detected any abnormalities in recent fog occurrences in Canada”.
Snopes discussed the topic with Ismail Gultepe, a professor at the Ontario Tech University specializing in cloud physics. A significant part of his scientific career was spent studying the phenomenon of fog. He explained that fog formation requires humidity in the air, cooling temperatures, and aerosols. Aerosols, or particles of liquid or solid substances in the air, serve as nuclei for water vapor that condenses as temperature decreases. Therefore, fog is a common occurrence in winter. Air pollution can also act as an aerosol. He explained that fog sometimes occurs accompanied by air pollution, which may explain the “unpleasant smell” reported by people. When pollution remains “trapped” in a water droplet, concentrated molecules can cause unpleasant odors and persist in the air.
Responding to the question about the “unusual shining particles” of fog, Gultepe emphasized that there is nothing suspicious about it because most videos are made at night when additional lights are used for filming, either on the camera or from the side, creating glare. He added that he also has such nighttime videos from his own research.
He also addressed the information that some people felt unwell due to fog, could not sleep, or developed cold symptoms. He told Snopes that something like this can happen: “If there is a source of pollution or if you are in a city with high levels of pollution from exhaust gases, and then you breathe it in, it can have negative health consequences”. Some may develop a more pronounced cough, and some may have asthma. This is especially true for children, as research from 2003 has shown.
In conclusion, numerous posts about the “mysterious fog” recorded in several countries worldwide at the end of 2024 and the beginning of 2025 lack context, while those claiming it was artificially created are false. Fog is a common winter occurrence, and there is no evidence that this time was different. Experts agree that for some people, especially those prone to respiratory problems, fog can be a concern, but it remains a typical winter phenomenon.