Official Météo-France observations recorded a daily maximum of exactly 29°C in Paris on July 31, 2026, anchoring the market at 100% implied probability for that outcome. This reading aligns with surface station data under standard World Meteorological Organization protocols, reflecting modest afternoon insolation beneath a weakening high-pressure ridge, limited boundary-layer mixing, and urban heat-island effects that added roughly 1°C relative to rural surroundings. Ensemble guidance from ECMWF and GFS had converged on the 28–30°C range in the final model runs, with the precise 29°C threshold hinging on observed peak timing and minimal cloud cover. A post-event verification error at the primary Paris-Montsouris station or an atypical microscale advection shift could theoretically reopen uncertainty, though such revisions are exceedingly rare once certified data are published.