Wind surfing and kite surfing are popular sports in The Netherlands, and it is visited by water and wind tourists all year through. There is lots of water, good beaches and usually wind. Although there are some (weak) thermal winds around the IJsselmeer and in the coastal areas, the wind in The Netherlands is mostly influenced by the movement of weather systems (depressions) over Europe. Hence the wind is reasonably predictable within a week or so, but longer forecasts are not possible. For stronger and less gustly winds surfers pick the spots where the wind blows from the sea or from the IJsselmeer without any obstruction.
Many of the lakes, including some beaches around the IJsselmeer lake have far stretching shallow water, which is practical for beginners and sometimes a bit cumbersome for advanced surfers.
The water temperature always requires you to wear a suit, except in hot summers on the lakes. In winter only the real die hards and professionals go out to surf.
Kite surfing is only allowed at designated spots; in practise this means that, to avoid collisions, kite surfers are not allowed to share water and beaches with lots of other people. There are plenty kite surfing spots at the moment. The same goes in principle for wind surfing, but since there are less practical issues you are usually allowed to surf anywhere where there is no commercial water traffic.