UK marine heatwave forecast to reach extreme levels next week

Surface waters across north-west European seas are experiencing moderate to severe marine heatwave conditions, with many areas classified as strong and some as severe, according to the Met Office. Temperatures have already reached levels normally seen in August and are on average 2C above the seasonal norm.

Some offshore regions along the English and Welsh coasts are more than 4-5C warmer than usual.

Recent heat dome and record temperatures The current marine heatwave follows last week's heat dome that produced the hottest June day on record, exceeding the previous mark set in 1976 by more than 1C. After a brief cooler period, forecasters expect temperatures to rise again next week, with parts of South East England potentially exceeding 30C.

Limited cooling time for sea surfaces increases the chance the marine heatwave reaches an extreme classification, a level rarely recorded in UK waters.

Regional conditions and expert statements The English Channel has experienced marine heatwave conditions for much of 2026. Surface temperature anomalies in parts of the North Sea are forecast to peak at 4-5C above average in the coming days. An air-sea interaction specialist at the Met Office stated that such conditions would be highly unusual for UK waters and that marine heatwaves have developed rapidly following the recent heat dome.

The EU's Copernicus Climate Change Service and Copernicus Marine Service confirmed that global sea surface temperatures have surpassed previous records for this time of year set in 2023 and 2024.

Ecosystem and public safety notes A principal scientist at the Government's Centre for Environment, Fisheries and Aquaculture Science said prolonged warm sea temperatures can shift fish populations, damage seagrass and kelp habitats, and increase harmful algal blooms.