Dutch people. Peoples of the North, who lack a strong cultural awareness of how to handle heat waves. Please heed my words

1) Pull all the curtains closed. Reflect sunlight away from the windows. Tape up a bedsheet or something if you don't have curtains or blinds (not that rare in the Netherlands)

2) Open windows on opposite walls of the house, prop open the interior doors with something heavy, get a cross-breeze going. (Yes, the curtains may get flappy. I tucked the end of a long one under my bed mattress to mitigate this)

3) Take a quick shower with water that is only slightly warmed (neither ice cold nor steaming hot). Do this two, three, four times a day if you have to.

4) Similarly, drinking water that is ice cold may sound good but it's liable to give you stomach cramps when you're very hot. Your drinking water shouldn't be more than slightly cool.