**Official meteorological observations confirmed a daily maximum of 28°C in Paris on September 25, 2026, driving the near-certain market consensus.** Clear skies, light southerly winds, and strong solar insolation produced a pronounced diurnal rise from morning lows near 15°C, consistent with multiple forecast models and surface station data that aligned on this peak. This value exceeded the long-term average high of about 20°C for the date while remaining within plausible late-summer variability under stable high-pressure conditions. Trader positioning reflects the resolution criteria tied to authoritative records, with only narrow scenarios—such as post-hoc station adjustments or differing measurement protocols—potentially altering the exact threshold.