The Sea Writes the Weather Before It Appears in the Sky

When we speak of weather, we almost always think of wind, clouds, rain or atmospheric pressure. Yet a substantial part of what happens in the sky begins silently at the surface of the sea.

Water temperature determines how much heat and moisture the ocean transfers to the atmosphere. Warmer seas encourage greater evaporation, fuel cloud formation, increase the energy available to low-pressure systems and storms, and can lead to more intense rainfall. Colder waters, by contrast, tend to stabilise the lower layers of the atmosphere. Often, however, the contrast between different bodies of water matters even more than their absolute temperature. When a low-pressure system crosses an area with sharp temperature differences, it can intensify rapidly and cause unexpected changes in both the wind and sea conditions.

This is precisely why 2026 has been such a difficult year to interpret. In February, the central and western North Atlantic were experiencing colder waters, while exceptionally high temperatures were being recorded in the subtropical Atlantic.

This thermal contrast may have contributed to the succession of storms that affected Europe. In the months that followed, average ocean temperatures once again approached record levels, until June recorded the highest value ever observed for that month: 20.86°C between 60° South and 60° North.

At the same time, the Pacific moved rapidly from relatively neutral conditions into a new El Niño event, which is expected to strengthen towards the end of the year. Although this is happening thousands of miles away, the change affects major atmospheric circulation patterns and ultimately influences rainfall distribution, temperatures, jet streams and even tropical cyclone activity in the Atlantic.

The apparent paradox of 2026 neatly illustrates the complexity of meteorology: a warm Atlantic provides more energy for tropical storms, while a strong El Niño can increase upper-level winds and make it more difficult for those storms to organise. Consequently, despite the high sea temperatures, the Met Office is forecasting a below-average Atlantic hurricane season, with approximately 12 named storms and five hurricanes.

For sailors, the conclusion is simple: it is no longer enough to look at the calendar and rely on the traditional behaviour of the seasons. Throughout 2026, the Atlantic has alternated between sharp thermal contrasts, temperatures close to historic highs and rapid changes in major oceanic patterns. A forecast issued five days ago can quickly become outdated, while an apparently stable weather window may close sooner than expected.

The sea is not merely where weather happens. It is one of the forces that creates it. In this year of constant change, understanding water temperature has become almost as important as knowing how to read the wind, atmospheric pressure and clouds.

At sea, the best rule remains the oldest one: observe, compare, update and never assume that tomorrow will behave like yesterday.