The temperature in the Netherlands topped 25 degrees at the Bilt weather station near Hilversum on Saturday, making it the first official ‘summer’ day of the year.

This is relatively early in the year, weather bureau Weerplaza said. On average, the temperature first tops 25 degrees around May 19.

The sea temperature is still a chilly 10 to 11 degrees, so swimmers are being warned there is a risk of hypothermia if they stay in too long. ‘Two days of sunny weather have not warmed up the water,’ a spokeswoman for the sea rescue brigade told news agency ANP. ‘Think in advance if you are fit enough to dive into cold water.’

The temperature in the Netherlands, Belgium and parts of Germany is currently warmer than most of the Mediterranean region and will remain so until Thursday, Weerplaza said.

Sunday will be similar to Saturday but on Monday there could be thunderstorms in the southern provinces Weerplaza said. The showers will spread nationwide on Tuesday.