The Netherlands is bedecked in orange and the famed national football team isn't even playing. Monarch Willem-Alexander is turning 48 and the whole country is celebrating King's Day.

The national holiday brought the king to Dordrecht, a city close to the port of Rotterdam, to set off a full day of celebrations under sunny skies among thousands of well-wishers in orange-coloured outfits.

The celebrations will end with hundreds of evening parties across the nation of 16.8 million. Highlight of the daytime celebrations was an armada of pleasure boats going down the river as Willem-Alexander, Queen Maxima and their three daughters were taken around in a vessel turned out with orange flowers.

Celebrating the monarch's anniversary has been a tradition for several generations in the Netherlands.