Met Éireann has confirmed that there has been a marine heatwave around Irish coasts during this month of May.
The heatwave, which is similar to that recorded in June 2023, could have an impact on marine life if prolonged.
Met Éireann said that high pressure and easterly winds contributed to average monthly sea surface temperatures around Irish coasts being between 0.6 and 2.2°C higher than average for this time of year.
Sea surface temperatures along Ireland’s western and southern coasts have been significantly above average throughout May 2025, it said.
Provisional observational data from the Irish Marine Data Buoy Observation Network (IMDBON), which is managed by the Marine Institute in collaboration with Met Éireann, show that the surface temperatures have been rising steadily over the month, it said.
While marine heatwaves are occurring in various regions globally, the particularly high anomalies in the eastern North Atlantic—off Ireland’s west coast—are striking, it said.
“Although this spring has so far been marked by dry weather due to the dominant high pressure, the unusually warm sea temperatures could contribute to increased rainfall intensity if atmospheric conditions change,”it said.
“A shift in the weather is expected in the coming days, with stronger westerly winds, coming from the Atlantic, forecast to return,”Met Éireann said late last week.
“These winds should help mix cooler subsurface water with the warm surface layer, potentially decreasing sea surface temperatures, at least temporarily,”it said.
“ However, the ocean is a slow-moving thermal reservoir compared to the atmosphere, so cooling effects may take time to occur, likely not becoming evident until the end of the month,”it said.
“Globally, rising ocean temperatures are a clear sign of climate change. As the atmosphere and oceans warm, the number and duration of marine heatwaves are projected to increase,”Met Éireann said.
“These events can have major ecological impacts, including coral bleaching, shifts in marine species, harmful algal blooms, and disruptions to food chains. While recent marine heatwaves around Ireland have occurred outside the typical peak sea surface temperature period in August, future events aligning with the warmest part of the year could place greater stress on marine ecosystems,”it said.
More details are on Met Éireann’s website here
