North Sea hits record 20.4°C amid marine heat wave

The North Sea hit an exceptional temperature on Wednesday morning. Seawater reached 20.4 degrees Celsius at 8 a.m. at a KNMI measurement station off the South Holland coast, setting a record for this time of year.

The sea has been under a heat wave since May 24. A high-pressure system now dominates the weather over the Netherlands. As a result, the unusually warm water is not yet generating cloud formation, a KNMI spokesperson said.

"In autumn, a warm sea can cause heavier rain showers," the spokesperson added.

The North Sea has warmed by about half a degree Celsius per decade since the 1980s. More than 90 percent of the extra heat trapped globally by the greenhouse effect is absorbed by seas and oceans.

This warming is shifting marine life. Sea creatures that typically live in more southern and warmer waters are moving into Dutch waters. At the same time, fish that prefer colder conditions, such as herring, are heading farther north.