METAR weather code reference for FU (Smoke)
Small particles suspended in the air from combustion, such as wildfires, industrial activity, or agricultural burning. Smoke can dramatically reduce visibility across large areas and may persist for weeks during wildfire season. It can reach very high altitudes and affect flight operations far from the source.
Here are common ways FU appears in real METAR observations:
FUFU HZFU BKN020These METAR codes are commonly seen alongside FU or describe related weather phenomena:
Fine dry particles of dust, salt, or other matter suspended in the atmosphere that give the sky a characteristic opalescent appearance. Unlike mist, haze particles are not water-based. Haze reduces visibility and is most common in warm, dry conditions. It can persist for days under stagnant high pressure systems.
Fine particles of earth or other matter raised from the ground by wind and suspended in the atmosphere. Widespread dust reduces visibility and is most commonly reported in arid regions. Dust events can cause significant restrictions to visibility and affect engine performance.
Fine particles of rock and glass ejected from a volcanic eruption and carried by wind. Volcanic ash is an extreme hazard to aviation because it can cause engine failure, erode windshields, clog pitot tubes, and contaminate aircraft systems. Pilots must avoid volcanic ash at all costs.