What does haze mean on the weather forecast?

Haze on a weather forecast means the air is full of tiny dry particles, such as dust, smoke or pollution, that make the sky look milky and cut how far you can see, with no rain, fog or cloud to blame. In US weather reports haze is coded HZ and is only reported when visibility falls below 7 miles (11 km). If the murk is made of water droplets instead, it is mist, and below 5/8 mile (1 km) it is fog. The sun can be out at the same time, which is why your app can say "haze" under a clear sky.

What is haze, in weather terms?

The National Weather Service (NWS) glossary defines haze as "an aggregation in the atmosphere of very fine, widely dispersed, solid or liquid particles, or both, giving the air an opalescent appearance that subdues colors." The World Meteorological Organization's International Cloud Atlas is stricter: haze is a suspension of "extremely small, dry particles invisible to the naked eye." The NWS observing handbook uses the same dry definition, and dryness is the practical dividing line: haze is particles, while mist and fog are water.

You can often tell them apart by color. The WMO says that through haze, distant bright objects look yellowish or reddish and dark objects look bluish. Mist forms a thin grayish veil, fog a whitish one, and the air in fog usually feels damp.

Haze vs mist vs fog vs smoke vs smog: what is the difference?

Smoke and haze overlap. The Federal Meteorological Handbook, the US standard for weather observations, says smoke can turn into haze after it has traveled great distances, 25 to 100 miles (40 to 160 km) or more, once the larger particles have settled out. So smoke from a distant fire can arrive as an even haze, while the WMO notes that smoke present in large quantities can be recognized by its smell. For the wet end of the table, see what a Dense Fog Advisory means.

How does a weather station decide it is haze?

In the US the call can be made entirely by a machine. The Automated Surface Observing System (ASOS), which its user guide describes as the primary surface weather observing system in the United States, does not see particles at all. It infers the obstruction from visibility, temperature, dew point and whether anything is falling:

1. Visibility must drop below 7 miles. Above that, no obstruction is reported.
2. If the dew point (the temperature the air would have to cool to before it is saturated) is within 4°F (about 2°C) of the temperature, the air is moist: the station reports mist, or fog below 5/8 mile.
3. If the gap is larger than 4°F and no precipitation is falling, it reports haze.
4. If the dew point reading is missing, 4 to 7 miles counts as haze and anything lower as mist or fog.

Two consequences follow. ASOS reports only four obstructions (fog, mist, freezing fog and haze), so smoke and dust appear only if a human observer adds them. At an unstaffed airport, smoke that cuts visibility in dry air is logged as haze. The guide also admits that real fog or mist with a dew point gap above 4°F is reported as haze.

A real example. At 8:56am CDT on October 12, 2026, the automated station at Norfolk, Nebraska (KOFK) reported AUTO VRB03KT 5SM HZ CLR 21/15. Decoded: wind variable in direction at 3 knots (about 3 mph or 6 km/h), visibility 5 miles (8 km), haze, no cloud detected below 12,000 feet, temperature 70°F (21.1°C) and dew point 59°F (15.0°C). The 11°F (6.1°C) gap is well past the 4°F line, so the station called it haze, not mist. An hour earlier it had reported 10 miles and clear skies.

Why does my weather app say haze when it is sunny?

Because haze and sunshine are not opposites. The NWS icon key includes "Fair with Haze" alongside "Partly Cloudy with Haze" and "Overcast with Haze", and Apple's haze icon is a sun above horizontal lines, not a cloud. Haze describes how far you can see, not how much of the sky is covered: in the Norfolk example the sky was cloud-free while visibility was down to 5 miles.

Apps then translate the same sky differently. Apple, the NWS, Australia's Bureau of Meteorology ("Hazy") and The Weather Company all have a haze icon. The UK Met Office has Mist and Fog symbols but no haze symbol, and the condition list Google publishes for its weather API has no haze or fog type at all. So one app may show haze while another shows plain sunshine for the same hour. It is the same pattern as forecasts disagreeing in general, and our US city forecasts put the sources side by side.

What causes haze?

The EPA's short answer: haze forms when sunlight meets tiny particles in the air, which absorb some of the light and scatter the rest before it reaches you. The particles come from:

• Natural sources: windblown dust and soot from wildfires.
• Human sources: motor vehicles, fuel burned by power plants and industry, and manufacturing.
• Gases that become particles: some haze is emitted directly, the rest forms from gases as they are carried many miles downwind.

Humidity makes it look worse. The EPA notes that some particles, such as sulfates, scatter more light in humid conditions, so the same amount of pollution can look thicker on a muggy day. Weather decides how much builds up: the NWS issues an Air Stagnation Advisory when pollution, smoke or dust is expected to build up near the ground, usually under a stagnant high-pressure system with weak winds that cannot bring in fresh air.

The cost to the view is large. The EPA says air pollution has substantially reduced visual range in national parks: in the East the average has fallen from 90 miles (145 km) to 15 to 25 miles (24 to 40 km), and in the West from 140 miles (225 km) to 35 to 90 miles (56 to 145 km). The page gives no year, so read these as the EPA's long-run comparison, not today's view. It adds that most of this haze is air pollution rather than natural.

Is haze weather dangerous?

Haze itself is a visibility report, not a health reading: the word tells you how far you can see, not what the particles are. Some of them matter. The EPA says some haze-forming pollutants have been linked to serious health problems, and that exposure to very small particles has been linked with increased respiratory illness, decreased lung function and premature death. The number to check is the Air Quality Index (AQI) at AirNow.gov:

• 0 to 50, Good: little or no risk.
• 51 to 100, Moderate: acceptable, with some risk for people unusually sensitive to air pollution.
• 101 to 150, Unhealthy for Sensitive Groups: sensitive people may feel effects.
• 151 to 200 Unhealthy, 201 to 300 Very Unhealthy, 301 and higher Hazardous.

When the haze is wildfire smoke, the EPA says the fine particles (PM2.5) can affect the lungs, heart and other organs, lead to asthma attacks and make COPD worse. People with heart or lung disease, older adults, children and teenagers, pregnant women and outdoor workers are at higher risk. For eye, nose or throat irritation, coughing or wheezing, the EPA's advice is to go somewhere with cleaner indoor air or wear a well-fitting particulate respirator such as an N95. Smoke can also cause severe problems, such as worsening heart and lung disease, and the EPA says to seek medical attention if they occur. People at increased risk should check with their health care provider about what to do during smoke events. The NWS also relays Air Quality Alerts issued by state and local agencies, and in fire season a Red Flag Warning is the other alert worth knowing.

What does haze mean on a UK or Australian forecast?

The Met Office forecast table has no haze symbol. Instead it rates visibility with a letter, from VP (very poor, under 0.6 mile or 1,000 m) to E (excellent, over about 25 miles or 40 km). A 5-mile (8 km) visibility, haze territory at a US airport, rates M, moderate (2.5 to 6.2 miles, or 4 to 10 km). In Australia the BOM has a Hazy icon, a sun behind brownish bands, drawn separately from its Fog icon, which uses pale bands.

Haze, in short, is the dry-air word: particles, not water, cutting visibility; US stations report it below 7 miles. Seeing it under a blue sky is normal. Whether it matters for your lungs depends on what the particles are, and the AQI, not the weather icon, is what tells you that. The same particles are why the sun can look red through haze or smoke, part of the story behind red sky at night.