Official KNMI observations at Amsterdam Airport Schiphol—the market's designated resolution source—confirm the highest temperature on April 20 reached exactly 12°C, driving trader consensus to a 100% implied probability on that outcome as provisional data solidifies post-midnight. This aligns with cool maritime airflow from northwesterly winds at 3 Beaufort, scattered showers, and cloudy conditions limiting solar heating, consistent with ECMWF model guidance from the prior 48 hours predicting highs in the 11–13°C range. Historical April norms around 13°C provide context, though recent weeks' variable spring patterns underscore measurement precision from automated sensors. Revisions remain theoretically possible if data audits reveal sensor anomalies, but such changes are exceedingly rare after 24 hours.