UK weather: What is a ‘heat dome’ and how will Brits be affected as temperatures soar to 32C this week

The UK is currently in the grip of a delayed heatwave, with temperatures predicted to hit a potentially record-breaking 32C over the coming days. While September usually signals the arrival of the colder months, Britain is set to be hotter than Athens (27C), Ibiza (28C) and Ayia Napa (30C) this week.

Soaring temperatures have sparked a yellow heat health alert from the the UK Health and Safety Agency, which will remain in force across most of England until Sunday night (September 10). But why is it so hot in the UK at the moment, and is a ‘heat dome’ to blame?

Why is it so hot in the UK at the moment?

The warmer weather is being linked to a jet stream which has brought largely unsettled weather conditions to the UK in recent weeks. The Met Office said the jet stream was continuing to shift north from Spain, allowing high pressure to build across the UK.

The influence of former tropical cyclone Franklin is also continuing to move into the north of the Atlantic, amplifying this build-up of high pressure. 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.”

What is a heat dome?

Forecasters have recently pointed out the formation of a “heat dome” over the western half of Europe, including countries such as France, the Netherlands and Belguim. 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, according to the Royal Meteorological Society.

This phenomenon causes temperatures “to keep building day on day” and rise above what is considered normal, since warm air becomes compressed over a smaller area. Although a heat dome is currently sparking higher than average temperatures in some Mediterranean countries, it is apparently not responsible for the heatwave we’re currently experiencing in the UK.

When will heatwave end in UK?

This weekend there is a chance of a “breakdown” in the settled conditions although the exact timing of this is uncertain. Temperatures are likely to return closer to normal during mid September, although they will probably still be above average.

From September 8 onwards, conditions are likely to become more changeable, with an increased chance of rain or showers for all areas, some heavy or thundery. In the second half of September, conditions are likely to vary across the country, with showery rain being most frequent in northwestern areas of the UK.

The Met Office long range forecast reads: “Confidence in the forecast decreases later in this period; however, a mix of mostly dry weather with occasional wet spells is possible, with a higher incidence of high pressure forecast. There is a greater chance than normal of temperatures being above average.”