A Marine Heatwave Sweeps Across the North Sea
A widespread marine heatwave developed across the North Sea in June and July 2026, supported by unusually warm air, increased solar heating and weakened winds.
By the end of June 2026, unusually warm water had spread across much of the North Sea. Sea surface temperatures were widely 1-2°C above the 1998-2025 average, with local anomalies approaching or exceeding 3°C in parts of the southern basin.
Figure 1. Rapid development of anomalous sea-surface warming across the North Sea. Mean SST anomalies relative to the 1998–2025 climatology are shown before the event (1–17 June; left) and during the broader marine-heatwave period (18 June–5 July; right). Warming intensified and expanded across the central and southern basin, locally exceeding 3°C.
During the first half of June, anomalies were moderate and spatially uneven. From 18 June onward, the warming intensified and expanded. A marine heatwave was detected from 20 June to 5 July, and at its peak approximately 60-65% of the analysed area was affected.
A full report is accesible here.
