**Strong model consensus on suppressed daytime heating has driven near-certain trader positioning at 20°C.** Numerical weather prediction runs from ECMWF and the Met Office indicate a cooler-than-average maritime air mass advecting over Istanbul under moderate northerly flow on June 13, limiting maximum temperatures to the 20–21°C range. This synoptic pattern, with associated cloud cover and reduced insolation, aligns closely with historical June climatology for the region when such flow regimes dominate. The 99.5% implied probability reflects the tight clustering of ensemble guidance around this narrow outcome, with minimal spread in forecast highs. Realistic challenges remain limited but include any late-day clearing that enhances solar heating or an unexpected shift to southerly winds, which could nudge the official station reading into the 21°C bucket; however, current observations and short-range guidance show low likelihood of such deviations before resolution.