If you’re superstitious - or you’ve seen the 1980 John Carpenter film or its 2005 remake too many times - you may have looked warily out the window yesterday around 5:30 p.m. as a soupy fog gathered over Boston.

Unlike in the horror movie “The Fog,’’ no ships were scuttled or sailors murdered, but yesterday’s fog did result in delays of over three hours at Logan Airport, according to the Federal Aviation Administration.

The major landmarks and tall buildings of Boston were nearly hidden. And if you felt like you were driving through a cloud, you were, literally.

Fog in the afternoon may seem odd, but there’s a scientific explanation.

The morning fog we’re used to is called “radiation fog.’’ At night the temperature drops and the earth is giving off energy. As the temperature reaches the dew point, fog forms.

Yesterday’s fog was different. It is called “advection fog,’’ and it forms over an already cool surface like water and is gradually carried inland by the wind.

Matthew Belk, a meteorologist with the National Weather Service in Taunton, said yesterday’s fog was some 30 miles in diameter, enough to linger in the Hub for several hours.

But it wasn’t a horror show.

John M. Guilfoil can be reached at jguilfoil@globe.com

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