**Observed maximum temperatures at Cape Town stations reached 18.9°C on September 12, 2026, driving the market's near-certain 19°C outcome.** Official meteorological data recorded a daily high of 18.9°C under overcast skies with light winds and minimal precipitation, consistent with multiple forecast models that converged on an 18–19°C peak during the afternoon. This aligns with the current late-evening readings near 16°C after the daytime maximum, confirming the daily high. The strong consensus reflects real-time surface observations from authoritative monitoring networks rather than projections. A shift would require an unreported station measurement exceeding 19.5°C or a significant revision in official records, both improbable given the consistency across sources and the day's stable synoptic conditions.