The Ministry of Transport and Mobility, through Puertos del Estado, has launched a new statistical indicator that provides daily average seawater temperatures along Spanish coasts and tracks their evolution since 2005. The new tool expands the oceanographic information currently available and strengthens the monitoring of a key parameter for assessing the effects of climate change on the marine environment.
The indicator is calculated using hourly measurements collected by the buoy networks managed by Puertos del Estado. Together, the Offshore Buoy Network and the Coastal Buoy Network comprise nearly 30 monitoring locations distributed across Spanish coastal and offshore waters.
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Transport launches an indicator to monitor sea temperatures along Spanish coasts and analyse the effects of climate change
The data are processed according to Marine Demarcations, geographical areas defined by similar oceanographic characteristics. This approach enables a more detailed territorial analysis of changes in seawater temperature. The system also provides a weighted national average calculated according to the kilometres of coastline represented by each Marine Demarcation.
Updated daily, the indicator shows the evolution of average daily seawater temperatures since 2005. According to the data processed so far, the highest national value was recorded on 25 August 2023, when the indicator reached 25.22°C. In 2025, the most recent year with complete measurements, the maximum was 24.15°C, recorded on 13 August.
By geographical area, the Mediterranean Levantine-Balearic zone recorded the highest average daily temperature, reaching 28.67°C on 23 August 2023. The maximum recorded in the Canary Islands was 25.78°C on 7 October 2024, while the Strait of Gibraltar-Alboran area reached 25.50°C on 31 August 2024. The South Atlantic zone registered 25.10°C on 18 August 2025, and the North Atlantic zone reached 22.26°C on 25 August 2023.
Monitoring sea temperatures is particularly important due to their potential impact on marine ecosystems, water quality, fisheries and certain industrial processes that use seawater. Changes in this parameter also provide valuable information for assessing the effects of climate change.
The new indicator complements the oceanographic services already provided by Puertos del Estado through its marine observation, measurement and forecasting systems. Its infrastructure includes an Offshore Buoy Network with 15 monitoring positions, a Coastal Buoy Network with 14 positions, a network of 45 tide gauges distributed along the Spanish coastline and nine high-frequency radar stations jointly owned and managed with other institutions.
These monitoring systems provide real-time information on marine parameters including wave height, currents and seawater temperature. Puertos del Estado manages and distributes the collected information, while hourly data recorded by the buoys are openly available through its oceanographic information services.