‘Taste of proper autumn’ to come this week in Aylesbury Vale

After a very mild start to last week with some summer-like minimum temperatures at night, Aylesbury Vale saw much chillier nights take hold by the weekend.

In fact, the Vale has seen its first air frosts of the season in more sheltered spots – an air frost simply being an air temperature below zero.

But the vast majority of us won’t have had temperatures below zero, with the coldest conditions reserved for what are known as ‘frost hollows’.

A frost hollow is simply a relatively low-lying and sheltered dip in the local topography. On a clear, calm night, we see the ground cool down faster than the air above it, so it’s actually colder at the surface than it is slightly above our heads.

This only occurs when it’s a calm night, and even a slight breeze can stir up the air enough to stop it becoming particularly cold at the surface.

If an area is well-sheltered, this cooling process can accelerate much further when compared to less sheltered areas nearby.

In addition, cold air is more dense than warm air, so this dense cold air can ‘drain’ into low-lying areas, strengthening the frost hollow effect. The difference in minimum temperatures can be really quite extreme on very cold nights with snow cover.

While we’re not at risk of many frosts in the coming days in Aylesbury Vale, we’ll certainly get a taste of proper autumn.

Deep areas of low pressure will continue to sweep by the UK and bring us spells of heavy rain and possibly strong winds at times.