Official observations from Météo-France's Paris-Montsouris reference station, the authoritative source for the city's climate records, confirm the highest temperature on May 3 reached exactly 21°C amid mild spring conditions with partly cloudy skies and light winds. This measurement, finalized in preliminary daily reports, aligns with ensemble forecast models from prior days predicting highs in the 18–21°C range under a stable high-pressure system over Western Europe, consistent with early May climatological norms averaging 18–19°C. Trader consensus at 100% implied probability reflects this verified data, backed by real capital. Realistic challenges would require rare data revisions from quality control—such as recalibrations or overlooked station readings exceeding the threshold—though urban reference sites like Montsouris rarely see adjustments post-publication. Final monthly climatology updates expected later this month.