Heat Dome Patterns and Rising Temperatures: Assessing the European Summer Climate

A “heat dome” weather phenomenon is expected to drive temperatures up to 44 degrees Celsius across parts of the country this coming weekend. According to the Agencia Estatal de Meteorología (AEMET), this high-pressure system is trapping warm air, creating a prolonged period of extreme heat that follows earlier record-breaking temperature spikes across the continent, which the World Health Organization (WHO) has linked to over 1,000 deaths since June.

What is a Heat Dome?

A heat dome occurs when a high-pressure system traps heat. As the American Meteorological Society (AMS) defines it, this is “a mass of air exceptionally warm at mid-latitudes during the warm season, associated with a synoptic-scale high-pressure zone at altitude.” This high-pressure zone can exert a dome effect on the underlying warm air mass, suppressing upward movement and the formation of clouds and precipitation. According to the AMS, in some cases, the descending air associated with high pressure at upper levels can produce additional heating by compression. The warm air at the surface under a heat dome can persist for several days, as the flow at altitude is usually calm and stagnant, especially when the high pressure at upper levels is characterized as a blocking anticyclone.

Forecasted Impact on the Iberian Peninsula

Meteorological models indicate that the upcoming heat wave will reach its peak during the day on Tuesday, with some regions experiencing temperatures 8 to 10 degrees Celsius above the average in wide areas of the western peninsula. AEMET identifies the valleys of the Guadiana and Guadalquivir as areas of particular concern, where temperatures are likely to exceed 40 degrees Celsius. The central, western, and southern portions of the peninsula face the most significant risk, with forecasts suggesting highs of 44 degrees Celsius. In northern regions, temperatures are projected to climb above 35 degrees Celsius.

The Risk of Tropical Nights

Beyond daytime highs, the persistence of these heat domes creates “tropical nights,” where temperatures do not drop below 20 degrees Celsius. In many affected areas, nighttime lows are expected to remain between 25 and 27 degrees Celsius.

Historical Context and Mortality Data

The current climate trend follows a series of record-breaking heat events in countries including the Netherlands, Belgium, Italy, Croatia, Bosnia, Albania, Switzerland, the Czech Republic, the United Kingdom, France, and Germany. Data from the Instituto de Salud Carlos III confirms that previous heat waves this summer contributed to over 300 deaths in Spain. The WHO has noted that the majority of the 1,000+ fatalities recorded across Europe occurred in France.

Key Takeaways

• Heat Dome Mechanism: High-pressure systems trap warm air and compress it, preventing cooling and cloud cover.
• Temperature Forecast: Peak temperatures are expected to reach 44 degrees Celsius in parts of the country starting Sunday, July 5.
• Health Impact: Authorities are monitoring the rise in “tropical nights,” where temperatures stay above 20–27 degrees Celsius, limiting recovery from daytime heat.
• Regional Scope: While the Iberian Peninsula is currently the focus, similar high-pressure patterns have affected broad swaths of Europe throughout the summer.