Read the fog layer carefully
Check the time and the provider's legend before interpreting the shading. This view selects a modelled fog layer; do not read its colours as an independently measured distance in metres unless the selected product explicitly gives that quantity.
Fog consists of tiny water droplets near the ground that reduce visibility. Low cloud on a nearby hill can have a similar practical effect for someone inside it, while conditions in the valley below may differ.
Small areas can change quickly
Fog can form or clear locally as temperature, moisture and wind change. A model grid cannot represent every hollow, riverbank or sheltered street. A blank-looking area therefore does not guarantee good visibility at the roadside.
Compare neighbouring places and several times around your journey. Night and early-morning conditions can differ from the afternoon, and coastal fog may behave differently from fog formed over cooling land. A single frame is only part of the picture.
Combine forecasts with current conditions
For travel, check road updates and the conditions you actually encounter. Use the local temperature, wind and cloud forecasts to understand the wider setting, and follow official fog or freezing-fog warnings when issued. In the colder months, reduced visibility can coincide with other winter hazards. For aviation, marine navigation or mountain decisions, use the relevant specialist service rather than treating this general map as an operational visibility report.
Questions about this map
Is this a fog radar with live visibility measurements?
No. It presents model guidance for fog. Measured visibility is a separate observation and can vary substantially over a short distance.
Why is there fog when the map looks clear?
Local fog can be smaller than the model grid or develop between forecast steps. Always give current local conditions priority over the map.