What to Know About 'Mysterious Fog' Over Parts of Globe

As a persistent fog blanketed parts of the U.S., Canada and even the U.K., rumors began to spread in late 2024 and early 2025 that it may be nefarious, with people claiming the fog appeared to be made up of particles, that it smelled bad, and that it made people and animals ill. 

For example, a TikTok video posted from Florida in November 2024 went viral (archived):

As of this writing, the post had garnered 3.5 million views and 160,500 likes. The man in the video said the fog smelled "like after you set off a bunch of fireworks," and that the taste of the air was "toxic."

On Dec. 31, 2024, one woman in Florida also claimed on TikTok that the fog was making her sick. Another posted from Cleveland, claiming there was a chemical fog over the city. Another video, meanwhile, claimed that the fog came from Chinese drones that emitted it (Snopes examined the claims of drone sightings in the eastern U.S. in December 2024).

Reports of a "mystery fog" weren't confined to the U.S. On Jan. 6, 2025, in Vancouver, Canada, someone shared a video of the fog moving at night in the wind, describing it as a "thick chemical mist" that smelled "like nail polish remover." Claims also came from the U.K. A TikTok video claimed on Dec. 29, 2024, that London was "shrouded in smog" — a word that combines "smoke" and "fog" in reference to the polluted air that covered the city in 1952. A video claimed to compile night videos of the fog in the light of torches, showing rapid movement of supposed "particles" that left a "white residue." Allegedly, those videos were taken in Florida, Toronto in Canada, Georgia in the U.S., and London in the U.K. 

On YouTube, a video compiled several TikTok videos and speculated that the fog was killing animals:

The video claimed that the fog was global and it caused "sore throats, dizziness, nausea and even full body aches" and that "entire households were falling sick." It added:

Let's not stop there. Let's dig deeper, especially when it comes to the strange behavior of animals that has been reported across the globe: flocks of birds flying in wild, erratic patterns; entire schools of fish mysteriously washing ashore; even household pets — dogs, cats and other domestic animals — acting restless, agitated, almost as if they sense something we don't. Are these behaviors coincidental or are they connected to the bizarre weather patterns we've been witnessing?

The Fog Is Not Unusual

However, an interview with a fog expert revealed that there was nothing unusual about the dense fog that covered parts of the globe. Snopes contacted Ismail Gultepe, an adjunct professor at Ontario Tech University who specializes in cloud physics. Gultepe spent much of his career studying fog.

Gultepe explained that fog needs added moisture in the air, cooling temperatures and aerosols. Aerosols act as nuclei for water vapor to condense on as temperatures drop. In winter, therefore, fog is quite common. Pollution, too, can act as aerosols. 

"Usually in atmosphere you have aerosols naturally," Gultepe said. "And sometimes fog happens together with the pollution."

Asked for an explanation about smells, Gultepe said pollution may be the culprit there, too. When water droplets trap pollutants, they can concentrate molecules that cause odors and allow them to stay suspended in the air. 

Regarding questions internet users had about the fog being made up of unusual particles, Gultepe said there was nothing suspicious about videos filmed at night using torch lights. "Because of flashlight reflection, backscattering, you can see many small particles," Gultepe said. "But these are not necessarily suspicious. They are very small droplets." Gultepe said he made similar night videos of fog during a study project he carried out on Sable Island, off the eastern coast of Canada.  

Gultepe said that it wasn't unusual for fog to leave residue, either. This can happen with fog that comes in from the ocean, Gultepe said: "When the fog falls down, it deposits salt particles on surfaces, because there are salt in those the droplets." He added that this could happen with pollutants or other aerosols, as well. 

Lastly, regarding the fact that the fog was making people sick, Gultepe said that it could happen. "If there is a pollution source, or you are in a city with exhaust gasses, and then if you breathe this with the vapor, it can be bad for you." Further, a person might develop a cough when inhaling water vapor, or for some people, even asthma. Kids, in particular, can be susceptible, according to a 2003 article in the Journal of Asthma.

In short, none of the videos and claims that Snopes reviewed pointed to an unusual type of fog.