Flights Delay

Fog swirled into some parts of Boston this afternoon, causing flight delays at Logan International Airport.By 8 p.m., some arriving flights at the airport were being delayed by an average of 3 hours and 15 minutes due to the fog, the Federal Aviation Administration said on its fly.faa.gov website. Those delays, in turn, were causing some departure delays,travel agency said.

One reader wrote the Globe an email wondering about the fog, saying, There is a FIRE or something downtown right now. What is going on?Fire department spokesman Steve MacDonald said there was no fire, but there was plenty of fog.

Driving toward the city, a reporter could barely see the tall buildings.The fog is a type called “advection fog that forms over an already cool surface like the water and is gradually carried inland by the wind. Advection fog can form any time during the year.

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