👁️ Visibility
--km
Detecting your location…
How far you can clearly see — affected by fog, haze, rain, snow and dust. Critical for driving, aviation and sailing.
Visibility is the greatest distance at which objects can be clearly seen and identified. It is one of the most important weather variables for safety — for drivers, pilots, sailors and anyone moving through the landscape — because it can fall from many kilometres to a few metres in minutes when fog, heavy rain or snow set in.
We see distant objects by the contrast between them and their background. Anything that scatters or absorbs light along the path reduces that contrast. Tiny water droplets in fog and mist are the most common cause; rain, drizzle and snow scatter light too; and solid particles such as dust, smoke, haze and pollution can cut visibility over wide areas for long periods.
Fog is simply cloud at ground level — water vapour condensed into suspended droplets when air cools to its dew point. Radiation fog forms on clear, calm nights as the ground loses heat. Advection fog forms when warm, moist air moves over a cold surface, such as the sea or snow. Both can reduce visibility to a few metres and clear quickly once the sun or wind returns.
Stopping distances do not shrink in fog, but the distance at which you can see a hazard does, so visibility directly governs safe speed. Aviation has strict visibility minimums for take-off and landing, and shipping relies on visibility readings alongside radar. This is why accurate, location-specific visibility is a genuine safety tool, not just a curiosity.
Human observers traditionally judged visibility against known landmarks at measured distances. Today, instruments called transmissometers and forward-scatter sensors measure how much light is scattered or lost over a short path and convert that into a visibility distance. Forecast models estimate visibility from humidity, cloud and precipitation, as shown here.
By convention, it is called fog when visibility falls below 1 kilometre and mist when visibility is between 1 and a few kilometres. Both are suspended water droplets; fog is just denser.
Above about 10 km is considered good, and above 20 km is excellent, with distant hills and buildings sharply visible. Below 4 km indicates noticeable haze, mist or precipitation.
Radiation fog usually burns off as the sun warms the ground and the air, raising its temperature above the dew point so the droplets evaporate. Wind can also mix it away.
Yes. Haze from fine particles and smoke scatters light and can cut visibility over large areas for days, and it often coincides with poor air quality.