Marine heatwaves occur when ocean temperatures remain extremely high for prolonged periods, with serious consequences for marine ecosystems and the coastal communities that depend on them. Extensive marine heatwave conditions affected much of the Australian coast, contributing to coral bleaching on both eastern and western reef systems simultaneously - a first on record! During the 2024–25 summer, prolonged marine heatwaves contributed to ecosystem disruption, fish kills, and a severe harmful algal bloom in South Australian waters, with major impacts on aquaculture and fisheries. Marine heatwaves are becoming more frequent, longer-lasting, and more intense across the South-West Pacific. bureauofmeteorology and csirogram developed an operational marine heatwave prediction service providing forecasts up to three to four months ahead. The service enables marine managers to move from reactive responses to proactive risk management. Learn more about it in the WMO #StateofClimate in ...