What does atmospheric pressure have to do with autumn?

Pressure is key to understanding the UK’s changeable weather. But what exactly is atmospheric pressure, and how does it affect the changing seasons?

Autumn is coming, as atmospheric pressure changes

Talk of high and low pressure is a regular feature of weather forecasts. Pressure varies from place to place and over time, with its position and movement influencing our weather.

Meteorologists monitor pressure to see not only what conditions are approaching, but why the forecast is changing.

Experts from the Met Office explain how it influences the changing seasons at this time of year.

Meteorologists are particularly interested in areas where pressure is higher or lower than the surrounding atmosphere, rather than simply looking at one pressure reading in isolation.

What is atmospheric pressure?

Atmospheric pressure is the force exerted by the earth’s atmosphere on its surface. Pressure systems are closely linked to the vertical movement of air.

In an area of low pressure, air rises through the atmosphere. As it rises it cools, and water vapour condenses into cloud and rain.

Low-pressure systems occur when air circulates anticlockwise around a depression in the northern hemisphere.

High pressure, also known as an anticyclone, happens when air sinks. This limits cloud development, often bringing drier and more settled conditions.

However, high pressure does not always guarantee blue skies. During autumn and winter, moisture can become trapped near the surface beneath the sinking air.

With lighter winds and less daytime heat, low cloud, mist or fog may persist, producing what is sometimes described as anticyclonic gloom.

The Met Office expects