Some places have a foggy reputation. San Francisco fogs, for example, enjoy worldwide fame, and London fogs are legendary, or at least they used to be.
In the latter case, the diarist John Evelyn, writing in 1661, complained: "The city of London resembles more the face of Mount Etna, the Court of Vulcan or the suburbs of hell than an assembly of rational people.
"For when in all other places the air is most serene and pure, it is here eclipsed with such a cloud of sulphur that the sun itself, which gives day to all the world beside, is hardly able to penetrate and impart it here."
But neither London nor San Francisco can claim the doubtful honour of being the foggiest spot on the entire planet.
That accolade goes to Cape Race on the southern corner of the island of Newfoundland, where the Atlantic is obscured by fog for an average of 160 days a year.
Its vulnerability in this respect can be traced to the warm moist air sweeping northwards along the east coast of the United States and encountering the cold surface waters of the Labrador current flowing south from Greenland.
Fog itself, by internationally agreed definition, describes a situation where visibility is less than 1,000 metres, or about two-thirds of a mile. If the visibility is somewhat reduced, but remains greater than 1,000 metres, the obscuring medium is called a mist.
Sometimes, however, just to cause confusion, people will refer to a light drizzle as a mist, a faux pas that makes a meteorologist recoil in horror.
Neither is San Francisco even the foggiest spot in the United States. The foggiest place on the west coast is the aptly-named Cape Disappointment in the state of Washington, where it is foggy nearly 30 a cent of the time, or an average of 2,500 hours a year.
On the US eastern seaboard, its record obscurity of 1,500 hours of fog a year may also explain the name of Mistake Island, off the coast of Maine.
By these standards, fog in Ireland is comparatively rare. Strange as it may seem, the west coast of Ireland is foggy for only 30 to 60 hours a year, with a strong tendency for more fog to occur during the late spring and summer than in the months from September to March.
By contrast, inland regions are most foggy from October to January, and the phenomenon occurs more frequently than it does near the coast; a typical inland location in Ireland might experience fog for, say, 250 hours a year.