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Live forecasts update automatically; written guidance last reviewed 16 June 2026 by the Story Native weather desk. Data from national met services via Open-Meteo.
A moderate fog warning means the Met Office expects widespread fog to reduce visibility to between 100 and 200 metres, enough to disrupt driving, flights and ferries. These warnings are most common in autumn and winter when clear nights and light winds let fog form and linger into the morning.
What does a moderate fog warning mean for travel?
Visibility below 200 metres forces drivers to slow down significantly and use dipped headlights or fog lights. Motorway speed limits may drop to 40 mph, and some airports delay or cancel flights. If you need to drive, allow extra time and keep a greater distance from the vehicle ahead.
How long does fog typically last on a warning day?
Radiation fog – the type that triggers most moderate warnings – usually forms overnight and clears by late morning as the sun warms the ground. In coastal areas, sea fog can persist all day. Check the 10-day forecast for visibility trends in your region.
Is it safe to drive in moderate fog?
If you must drive, yes – but only if you reduce speed, keep a safe gap and use dipped headlights or fog lights. Do not use full beam: it reflects off the fog and makes visibility worse. Pull over if conditions feel unsafe.
Can a moderate fog warning be upgraded?
Yes. The Met Office may raise it to a severe fog warning if visibility falls below 50 metres, causing near-zero visibility. This is rare but possible when fog thickens over several hours or mixes with low cloud.
Does a moderate fog warning affect flights?
It can. Major airports like Heathrow and Manchester enforce reduced landing rates during fog, which often leads to delays. Check your airline’s status before travelling. For wider disruption, visit the UK weather hub.