{"icao":"KIAD","name":"Washington Dulles International Airport","lat":38.9445,"lon":-77.4558,"country":"US","tz":"America/New_York","updated":"2026-09-04T14:25Z","window":{"start":"2016-01-01","through":"2026-08-15"},"climatology":{"subCat1HoursPerYear":32,"bandDefinition":"visibility < ~800 m OR ceiling < 200 ft","fogSeasonPeakMonths":["January","December"],"monthlyHours":[8,5,3,0,1,1,0,0,1,3,2,7],"medianEventHours":2,"season":{"summary":"Fog season runs October through March, peaking in January; fog is mostly a 5 AM\u20139 AM phenomenon; typically thinning out by 11 AM; a typical event lasts about 2 hours (local time, 10-year average).","months":["January","February","March","October","November","December"],"timeOfDay":"5 AM\u20139 AM","typicallyClearsBy":"11 AM"}},"forecast":{"covered":true,"public":false,"cycle":"2026-09-04T13:00:00Z","guidanceSignal":false,"wording":"No fog signal in NWS guidance for the next 48 hours. September typically brings about 1 hour of dense fog here."},"links":{"page":"https://fogatlas.org/fog/kiad/","liveForecastApi":"https://fogatlas.org/api/forecast","liveObservationsApi":"https://fogatlas.org/api/metar?ids=KIAD","hourlyClimatologyDetail":"https://fogatlas.org/data/detail/KIAD.json","verification":"https://fogatlas.org/fog/scorecard/","methodology":"https://fogatlas.org/#methodology"}}