The market's decisive 100% implied probability on a 12°C high for Amsterdam on May 16 reflects the official maximum temperature recorded at the city's primary meteorological station, as reported by the Royal Netherlands Meteorological Institute (KNMI). With the observation period now complete, real-time surface data and quality-controlled readings have locked in this value, leaving no room for further atmospheric shifts. Traders recognize that post-event verification eliminates forecast uncertainty, though rare revisions from station calibration checks or micro-climate adjustments could theoretically alter the final figure if discrepancies emerge in the next few days.