Traders assign nearly equal implied probabilities to 28°C and 29°C as the highest temperature in Paris today because official forecasts from Météo-France and supporting ECMWF model runs show peak readings hovering right at the boundary between these values within a mild late-September air mass. Subtle variations in boundary-layer mixing, light winds, and urban heat-island effects at the reference station can easily shift the daily maximum by one degree, while limited cloud cover permits modest daytime warming. Lower and higher outcomes remain at minimal market-implied odds given the narrow forecast spread and absence of strong frontal passages or significant model divergence.