There is even a small chance of a heat wave, says Schröder. For this, it must be at least 25 degrees in De Bilt for five days in a row, three days of which are 30 degrees or more. Yesterday it was 28.8 degrees and that limit was therefore not reached. Today and the days to come will be tense. “For that heat wave, it makes a big difference whether it will be 29.9 or 30.1 degrees.”