The heavily urbanised core of Malta was up to four degrees warmer than rural spots in the west of the islands, a data scientist found in measurements taken on two days earlier this month.

Charles Mercieca was curious to explore the phenomenon of ‘urban heat islands’ across the country.

Using satellite data from the EU’s Copernicus Programme, he was able to calculate the land surface temperature.

His readings showed larger temperature differences between certain areas at night than during the day, which was also most apparent when the wind was weak.

The data was gathered for August 12 last year and for February 5, March 21, June 14 and June 16 this year. All temperatures were taken at 11 pm.

How urban heat impacted temperatures across Malta. Graphics: Charles Mercieca

According to Mercieca’s visual maps, the heavily urbanised areas around the harbour were distinctly warmer than their surroundings in August and June.

On the evening of June 16, Valletta, Floriana, Birkirkara, Msida, Ta’ Xbiex and Sliema were 23°, which was 2-3° warmer than their immediate surroundings and 4° warmer than the coolest spots, mainly in western Malta and western Gozo.

The urbanised areas around Marsaxlokk also stood out from their surroundings. The map shows a higher temperature for a ‘mini’ urbanised area in Buġibba.

In contrast, Attard, Balzan, Dingli and Mdina all had temperatures of around 19°.

In Gozo, Għarb, San Lawrenz and Żebbug had temperatures of 20°-21°. Areas in Għajnsielem and Sannat recorded slightly higher temperatures of 22°.

The same phenomenon could be seen on August 13, 2020, except that high temperatures were also observed along the Western coast, in areas such as Dingli cliffs.

On February 5, St Julian’s and parts of the Marsaxlokk coast were still 2-3° warmer than less urbanised areas.

The difference in temperature between urban and less-developed rural areas is down to how well the surface can absorb and hold heat. Structures such as high rises, parking lots and roads made of concrete and asphalt absorb and release heat more than natural landscapes.

In less developed areas, where more trees and farmland are found, water stored in such plants is released into the air and acts as nature’s air conditioner, making such areas cooler in temperature.