London weather: The difference between fog and mist, according to the Met Office, when the London outlook blurred this morning

Most Londoners woke up to find tiny drops of water clinging to their windows, and the usual view outside cut off drastically this morning (Saturday, October 9).

The rainstorm that surrounds the city is particularly dramatic in central London, where the usual views of the city’s most iconic skyscrapers have been totally hidden.

Which raises the age-old question – is the white carpet over London fog or mist?

READ MORE: Met office changes about snow on Halloween as temperatures drop in late October

Fortunately, Met Office has cleared this up for us with some practical guides on the difference between the two – as well as what separates them both from ‘haze’.

Met Office describes how fog and mist vary depending on how far you can see through them.

The Met Office website says, “Fog is when you can see less than 1,000 feet away, and if you can see beyond 1,000 feet, we call it fog.”

What we see today is therefore Fog, the Met Office weather forecast has confirmed.

Londoners can expect today’s weather to be marked by “Fog patches coping with hot periods of sunshine.”

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Both fog and mist are the result of water droplets suspended in the atmosphere at different densities, while haze is a completely different phenomenon.

Here are the full Met Office descriptions of fog, mist and haze:

Fog

In our meteorological glossary, fog is defined as ‘turbidity in the surface layers of the atmosphere caused by a suspension of water droplets’.

By international agreement (especially for aviation purposes) fog is the name of the resulting visibility less than 1 km.

However, in public forecasts, this generally refers to visibility less than 180m.

Fog

Fog is defined as ‘when there is such turbidity and the associated visibility is equal to or exceeds 1000 m.’

Like fog, fog is still the result of suspension of water droplets, but simply at a lower density.

Fog is typically faster to disappear and can quickly disappear with even light winds, this is also what you see when you can see your breath on a cold day.

Haze

A third term you may also hear mentioned is haze.

This is a slightly different phenomenon, which is a suspension of extremely small, dry particles in the air, not water droplets.

These particles are invisible to the naked eye, but sufficient to give the air an opalescent appearance.

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