Recent ensemble forecasts from the Turkish State Meteorological Service, ECMWF, and GFS models indicate Istanbul’s May 18 high will likely fall in the 19–22 °C range at the official Atatürk Airport station, producing the market’s tightly bunched probabilities around 20 °C. Mid-May climatology supports this with average maxima near 21 °C, moderated by persistent Black Sea sea breezes and partial cloud cover that limits peak solar heating. A weak high-pressure ridge over the region favors stable conditions, while any increase in afternoon insolation or slight southeasterly flow could nudge readings toward 22 °C; conversely, lingering low stratus would cap temperatures at 19 °C. Hourly model updates through the evening of May 17 and final 24-hour observations will determine the exact peak before resolution.