ieExplains: What is a heat dome? The phenomenon breaking temperature records across Europe

People enjoy the hot weather on Bournemouth beach in Dorset. Picture:PA

Ireland is set to see temperatures as high as 30C, while parts of Europe could see the mercury rise to 40C, with forecasters warning that a “heat dome” could bring exceptional heat.

France’s national weather agency said the record temperatures were caused by a heat dome, with hot air from Morocco trapped under an area of high pressure. 

It added that Europe could expect such events to “occur more and more often and earlier and earlier, and to be more and more intense”.

Models have already estimated that, because of climate breakdown, June heatwaves are now about 10 times more likely in Europe than they were in the preindustrial era. The same trend is also becoming visible in May.

So what is a heat dome, and how does it contribute to exceptional heat?

A heat dome is usually a dominant feature of summer weather patterns, occurring when a very warm air mass sits at a higher altitude. The air mass becomes “anomalously warm” at lower elevations and extremely hot near the surface.

According to meteorologists at Severe Weather Europe, the “heat dome” works like a lid on a pot.

"The extensive dome traps warm air at all levels underneath, with layers sinking toward the ground. Therefore, the air mass becomes anomalously warm at the lowest elevations and extremely hot near the surface," they said. 

The phenomenon, which moved northward from Africa, has now settled over western and central Europe.

"For late May, this is a historic, record-shattering heatwave. An extraordinary thermodynamic plume sends a massive core of extreme warmth over Spain, Portugal, Ireland, the UK, France, and Germany. Temperatures are soaring by 12-16C above long-term climatological norms," Severe Weather Europe said. 

"The strongest Heat Dome so far in 2026 is delivering mid-summer heat to millions of people well ahead of schedule. It is also well visible on the satellites, as a large blocking with drier air masses is gradually expanding north," they added. 

How does it affect daily life?

The excessive heat linked to heat domes can also "significantly impact human health and be dangerous to particularly vulnerable populations, such as elderly individuals, children, and those with pre-existing health conditions that can be worsened by extreme heat." 

The group warned that prolonged exposure puts construction workers, farmers, and other outdoor workers at increased risk of heat-related illnesses. It added that people living in poverty are often more vulnerable to fatalities because “their houses are often built with heat-trapping surfaces such as concrete and asbestos”.

- Additional reporting from the Guardian