What is a heat dome and will the UK be affected?

Some Mediterranean countries are experiencing hotter than usual weather due to the formation of ‘heat dome’

(Getty Images)

The UK is currently experiencing a delayed summer and surprise burst of sunshine, with temperatures predicted to rise to a potentially record-breaking 32C later this week.

This is around 4C hotter than Ibiza, and British temperatures are also set to be higher than Ayia Napa (30C) and Athens (27C) in Greece.

The UK Health and Safety Agency has issues a yellow heat health alert which will remain in force across much of England until Sunday night (10 September).

Met Office spokesperson Oli Claydon said: “The high temperatures are quite widely spread across the UK, although the highest temperatures are probably somewhere in south-eastern England spreading out to central parts of England as well.”

The unseasonably hot weather in the UK comes as parts of Europe are also seeing higher than normal temperatures for this time of the year.

Here, we look at what is causing a September summer across the region:

What is a heat dome?

Forecasters recently pointed to the formation of a “heat dome” over the western half of Europe, that’s ountries such as France, Belgium, the Netherlands, and Luxembourg

According to the Royal Meteorological Society, a heat dome is created when a high pressure area stays over the same region for an extended period of time – trapping very warm air underneath it, like a lid on a saucepan.

This weather phenomenon causes temperatures “to keep building day on day” and rise above what is considered normal, since warm air becomes compressed over a smaller region.

High-pressure circulation in the atmosphere acts like a dome or cap, trapping heat at the surface and favoring the formation of a heat wave (NOAA.gov)

While a heat dome is causing higher than average temperatures in some Mediterranean countries, it is reportedly not responsible for the UK’s ongoing Indian Summer.

Why is it so hot in the UK?

The warmer weather in the UK is being linked, not to a heat dome, but a jet stream, which has brought largely unsettled weather conditions to the UK.

High pressure conditions are building across the country over the week, as the jet stream shifts northwards.

Met Office Deputy Chief Meteorologist Mark Sidaway said: “An active tropical cyclone season in the North Atlantic is helping to amplify the pattern across the North Atlantic, and has pushed the jet stream well to the north of the UK, allowing some very warm air to be drawn north.”

Are we in the middle of a heatwave?

A heatwave is defined as three consecutive days with daily maximum temperatures meeting or exceeding the heatwave temperature threshold.

This threshold varies by county.

According to Sky News meteorologist Kirsty McCab, official heatwave conditions will be met in the UK this week “especially for southern parts of the country”.

However, this is likely to be the final spell of hot weather, as the Met Office said another heatwave is unlikely with temperatures set to return to normal by the second week of September.