The Foggiest Place on Earth

The foggiest place on Earth is the Grand Banks of Newfoundland, where fog is recorded on roughly 206 days a year. It happens because two of the Atlantic’s great currents collide there: the Labrador Current, carrying cold water and the occasional iceberg down from the Arctic, meets the Gulf Stream coming up warm from the south.

Warm, wet air slides over cold water, cools below its dew point, and the sea disappears. This site is named after that kind of weather, so we have taken the question seriously: where is fog thickest, why does it form there, and what has learned to live on it.

How fog forms, and why it picks favourites

Fog is a cloud that touches the ground. It forms whenever air is cooled to the point where it can no longer hold its water vapour, and the vapour condenses on dust and salt into droplets small enough to hang in the air. What makes one place foggier than another is how reliably that cooling happens, and there are four main ways it does.

Advection fog is the big one, and it is why every entry at the top of the list is on a coast. Warm, humid air moves sideways over a cold surface, usually cold ocean, and is chilled from below. The Grand Banks, Point Reyes, Cape Disappointment, the Namib and the Atacama are all places where a cold current runs close to shore and warm air blows across it. Radiation fog is the inland kind: on a clear, still night the ground radiates its heat to the sky, the air just above it cools, and by dawn the valley is full. This is Hamilton, the Po Valley and California’s tule fog. Upslope fog forms when air is pushed up a hillside and cools as it climbs, which is why mountain passes and the windward sides of islands are so often socked in. And evaporation fog, the steam that rises off a lake on a cold morning, happens when cold air moves over water that is warmer than it is.

Officially, it is fog when visibility drops below one kilometre. Above that it is mist. The distinction matters to pilots and to statisticians, and to almost nobody standing in it.

The Grand Banks: where two oceans argue

The Grand Banks are a series of underwater plateaus off Newfoundland’s southeast coast, shallow enough that sunlight reaches the seabed and rich enough in fish that Europeans were crossing the Atlantic for cod within a few years of Columbus. They are also where the Labrador Current, cold and southbound, runs straight into the Gulf Stream, warm and northbound. In summer the temperature difference between the two can be more than ten degrees Celsius across a few miles of water. The warm air above the Gulf Stream drifts north, hits the cold water, and condenses. The result is fog on more than half the days of the year, at its thickest in June and July, sometimes lasting for weeks without a break.

Argentia, a former naval station on Newfoundland’s Placentia Bay, is the individual weather station most often quoted for the world record, and St. John’s, the province’s capital, is the foggiest city in Canada by a wide margin. The fog is part of the culture there: the foghorn is a civic sound, and the province’s flag was designed to be seen through it.

Point Reyes and Cape Disappointment: the Pacific’s fog machine

The west coast of North America works on the same principle with a different mechanism. In summer, winds from the northwest push the surface water away from the California coast, and cold water wells up from the deep to replace it. Warm inland air is pulled toward the sea by the heat of the Central Valley, crosses that cold band, and turns into the marine layer. Point Reyes, the hook of land north of San Francisco, sticks far enough out into the cold water to log about 200 fog days a year, and its lighthouse was built 300 feet down the cliff, below the fog line, so ships could see it.

Cape Disappointment, at the mouth of the Columbia River in Washington, was named by a fur trader who could not find the river through the murk. Its weather station records around 2,500 hours of fog a year, the highest figure in the United States when measured by hours rather than days. San Francisco itself, with its famous named fog, has roughly half as many foggy days as the cape, but nobody has ever written a folk song about Cape Disappointment.

The deserts that drink fog

The strangest foggy places are the ones with no rain. The Namib, on the Atlantic coast of southern Africa, is one of the oldest and driest deserts on Earth, with parts receiving under 15 millimetres of rain a year. It is also fogged in on more than 100 mornings a year, because the cold Benguela Current runs along the shore and chills the sea air into a belt of cloud that drifts inland at dawn and burns off by mid-morning. The whole ecosystem is built on it. The fog-basking beetle climbs a dune before sunrise, faces the wind, tilts its body, and lets droplets condense on its shell and run down to its mouth. The Welwitschia, a plant that can live for a thousand years on two leaves, takes in fog through its stomata. Even the lichens are fog-fed.

The Atacama in Chile is drier still, and its coast has the camanchaca, a dense fog off the cold Humboldt Current that rolls in so reliably that people have learned to farm it. Fog catchers, large panels of fine mesh stretched between poles, intercept the droplets, which run down into gutters and tanks. A single panel can collect hundreds of litres on a good day; the village of Chungungo ran on fog water for most of the 1990s, and research stations at Alto Patache still do. The same idea has been exported to Morocco, Peru and Eritrea. It is the only place in the world where the weather is harvested with a net.

Fog in the valleys and the cities

Inland fog is a different animal, quieter and more seasonal. Hamilton, in New Zealand’s Waikato, sits in a river basin that fills with radiation fog on still winter nights and is routinely called the foggiest city in the country. The Po Valley in northern Italy was for centuries defined by its autumn fog, the nebbia that Fellini and Antonioni filmed, though it has thinned by about half in recent decades as the air has cleaned up and warmed. The Swiss Plateau spends much of the winter under a lid of Hochnebel, high fog trapped beneath an inversion while the Alps above it sit in sunshine. Chongqing, in central China, is nicknamed the Fog City for the mist that hangs over its two rivers. And Lima, one of the driest capitals on Earth, spends its winter under the garúa, a coastal fog so persistent that the city can go months without seeing the sun or a drop of rain.

Closer to home, the tule fog of California’s Central Valley is a radiation fog that forms after the first winter rains and can sit for days, and Mistake Island in Maine has recorded more than 1,500 hours of fog in a year, a reminder that the Labrador Current’s reach extends well south of Newfoundland.

What fog builds

The coast redwoods of Northern California grow where they do because of the marine layer. Their needles comb droplets out of the summer fog, which drips to the forest floor and is taken up by shallow roots; studies of the trees suggest a third or more of their water in the dry months arrives this way. The redwood belt stops almost exactly where the summer fog does. The same is true of the cloud forests of Costa Rica and the fog oases of the Peruvian coast, green islands in the desert that exist only because a hillside sits at the right height to catch the cloud.

Fog also built lighthouses, foghorns, the lore of every fishing town on the Grand Banks, and, in our case, a website. We named this place after the two things we find most beautiful in the Pacific Northwest, and the second of them is the one that makes the first grow. If you want the personal version of that argument, it is in In Praise of Fog, Our Namesake.

Fog questions, answered

What is the foggiest place in the world?

The Grand Banks of Newfoundland, with fog on about 206 days a year, are the usual answer, with the Argentia weather station as the specific record holder. Point Reyes in California is second at roughly 200 days.

What is the foggiest city?

St. John’s, Newfoundland is the foggiest city in Canada and a strong claimant worldwide. Hamilton in New Zealand, Chongqing in China, Lima in Peru and San Francisco are the other cities that come up, each foggy for a different reason.

What is the difference between fog and mist?

Visibility. Meteorologists call it fog when you can see less than one kilometre, and mist when you can see further. Haze is different again: it is made of dry particles like dust and smoke, not water droplets.

When is the best time to see fog?

Coastal advection fog peaks in summer, when the contrast between warm air and cold water is greatest: June and July on the Grand Banks, July and August at Point Reyes and along the Namib. Inland radiation fog is a cold-season event, at its best on still, clear mornings after a wet spell in autumn and winter.

Go deeper

For more of the planet’s strangest weather and landscapes, start with our guide to the natural wonders of the world and the Nature hub. For the Atacama in colour, see Gorgeous Visions of the Atacama Desert, and for what fog does to a landscape in a photograph, the Glossary entry on atmospheric perspective explains why painters have loved it since the Renaissance.