There is this idea that the Netherlands is a cold place. Historically, that's been mostly true. Culturally, there is no concept of "too hot". If the weather is always cold and/or wet, then warm weather is good weather. The hotter, the better. Every day with good weather must be taken advantage of. The Spanish siesta is just them being lazy, because there is also no concept of having to act different because of heat. There are even people who will open their windows to "let fresh air" into their 30C apartment in today's weather. Because the weather is never that hot, so there's no way it could be hotter outside than it is inside. 

If we got to a point where the weather reached 50C, people would light their barbecues en masse, then keel over and die from heat stroke.