If you’ve been following the Costa Blanca’s weather forecast this week, you’ve probably come across the phrase “heat dome”.
It’s one of those meteorological terms that suddenly seems to be everywhere, as forecasters warn of another spell of extreme temperatures across much of the country, including the Costa Blanca.
But what exactly is a heat dome, and why does it make hot weather feel even more relentless?
Costa Blanca heat dome
A heat dome develops when a large area of high pressure becomes established high in the atmosphere and remains almost stationary for several days.
Instead of allowing cooler air to move in, the high-pressure system acts like an invisible lid, trapping warm air close to the ground. As the sun continues heating the surface each day, that warmth has nowhere to escape.
The trapped air becomes compressed, causing temperatures to climb even further while preventing the atmosphere from cooling down properly overnight.
Meteorologists at the University of Alicante’s Climatology Laboratory note that this latest episode differs slightly from many previous heat events because it is being driven by an Atlantic ridge rather than a direct influx of hot Saharan air.
Is a heat dome the same as a heatwave?
Not quite.
A heat dome describes the weather pattern that allows extreme heat to build up, while a heatwave is an official classification based on strict criteria.
For Spain’s weather agency AEMET to declare a heatwave, unusually high temperatures must persist for at least three consecutive days across a significant part of the country and exceed thresholds considered exceptional for the time of year.
In other words, a heat dome can cause a heatwave, but it doesn’t automatically become one.
Why the Costa Blanca feels so uncomfortable
While inland areas of the Costa Blanca could see temperatures approaching 40°C over the coming days, many people along the coast will feel the heat even more intensely despite slightly lower readings.
The reason is humidity.
Warm, moisture-rich air from the Mediterranean makes it harder for sweat to evaporate from the skin, reducing the body’s natural cooling system and increasing the feeling of sticky, oppressive heat.
That’s why 32°C in Alicante, Benidorm or Torrevieja can often feel more uncomfortable than 37°C in the drier inland valleys.
Tropical nights return
The humidity also affects overnight temperatures.
Instead of cooling down after sunset, coastal areas often remain above 20°C, creating what’s known as a tropical night. In some places, temperatures may even stay above 25°C, producing so-called equatorial or torrid nights that can make sleeping difficult.
With the atmosphere remaining warm around the clock, buildings also retain more heat, making homes slower to cool overnight.
