**Trader consensus at 100% for an 18°C daily maximum in Warsaw on September 17, 2026, reflects the confirmed arrival of a cool frontal system that sharply reduced temperatures from the prior day’s 25°C peak.** Official observations and model consensus show a high near 18°C under mostly cloudy, rainy conditions with westerly winds limiting daytime heating, consistent with National Meteorological Service data and regional forecasts. This outcome aligns with climatological expectations for mid-September transitions in central Poland, where such fronts typically cap highs in the 16–20°C range. Remaining uncertainty is minimal this late in the day, though minor revisions could arise from final station readings or post-processing adjustments.