Greece is currently in the throes of an extraordinary heatwave, with temperatures soaring above 40 degrees Celsius in several regions. This extreme weather, unusual for this time of year, has led experts to issue urgent advisories, urging both locals and tourists to remain indoors during the peak heat of the day, stay well-hydrated, and steer clear of strenuous activities.
A drone equipped with a thermal camera recently soared over Athens, capturing the city as it sizzled in a severe heatwave. The images it recorded are nothing short of astonishing.
In the video aired by Greece’s public broadcaster ERT, dark purple hues highlight cooler areas, while lighter shades (red, orange, yellow) indicate significantly higher temperatures. During the heatwave, the temperature disparities between vegetated areas and those covered in concrete and asphalt become starkly apparent.
Green spaces are naturally cooler, whereas urban zones are much hotter, exacerbating the urban heat island effect. Notably, a drone operator recorded an astonishing temperature of 96.2 degrees Celsius in Omonia Square, at the center of Athens. ERT’s meteorologist emphasized the extreme temperatures car metal can reach under these conditions.
The “urban heat island” effect
The term “urban heat island” refers to the phenomenon where city centers exhibit higher air temperatures than the surrounding countryside. This temperature difference is usually more pronounced at night than during the day and tends to be more severe in winter compared to summer. Conditions of limited wind or calm weather further contribute to the formation of urban heat islands. Temperature differences can reach up to 15 degrees Celsius, depending on the factors causing the phenomenon.
Key causes include modifications to ground surfaces due to urban development and the generation of “thermal waste” from energy use (e.g., heating, vehicle traffic). The denser an area is built, the more heat is trapped by building materials, impeding air circulation. Building materials and asphalt have different thermal properties compared to natural elements in rural areas, emitting absorbed radiation differently. The high thermal conductivity and heat capacity of materials like concrete and asphalt prevent the urban environment from cooling quickly after sunset, resulting in significant night-time temperature differences between densely built areas and the countryside. The lack of greenery, heavy vehicle traffic, and pollutant emissions are also major contributors. The urban heat island effect has been notably recorded in major Greek cities such as Athens, Thessaloniki, Patras, Volos, and Heraklion.
This heat island effect, combined with the presence of polluting industries on the city’s outskirts and the region’s enclosed topography, leads to severe urban pollution. It facilitates the transfer of pollutants from the periphery, as air layers move to replace others rising due to the urban heat island effect.
