Trader consensus on Polymarket has locked in 17°C at 100% implied probability for Cape Town's highest temperature on April 21, 2026, driven by official South African Weather Service (SAWS) observations from Cape Town International Airport—the market's designated station—which recorded a maximum of 17°C amid partly cloudy skies and a passing cold front that limited solar heating and promoted cooler air advection. This aligns with seasonal autumn patterns in the Western Cape, where average April highs hover around 22–23°C but frontal systems often suppress peaks to 15–18°C, as seen in recent model guidance from SAWS extended forecasts. Realistic challenges would require a rare data revision from SAWS audits or evidence of station malfunction, though preliminary reports match independent records like 62°F (17°C) from nearby stations; final resolution awaits SAWS confirmation, typically within 24–48 hours.