**Forecast models and observations point to a maximum temperature in Warsaw on September 17, 2026, centered around 18–20 °C, aligning with the market’s leading outcomes at 19 °C (53.5 %), 18 °C (33 %), and 20 °C (12.5 %).** Widespread cloud cover, light showers or drizzle, and moderate westerly winds are suppressing daytime heating, consistent with official guidance from sources such as the Polish Institute of Meteorology and Hydrology and global models (GFS, ECMWF). September climatology for Warsaw shows typical highs near 16–19 °C; today’s pattern features higher humidity and reduced solar insolation compared with the clearer, warmer conditions on September 16 (when readings reached 24–25 °C). Recent model runs have converged on this narrow range, with only minor differences in timing of any brief clearing that could allow a brief spike toward 20 °C. Traders appear to weigh the high probability of rain (often 70–98 % in forecasts) and persistent stratiform clouds against the slim chance of partial afternoon sun, keeping implied probabilities tightly clustered around the observed forecast consensus. Updated short-range guidance later today could refine the exact peak if skies briefly clear.