**Trader consensus at 100% for a 20°C daily maximum in Warsaw on September 13, 2026, is driven by verified observational data from local weather stations showing a peak temperature of exactly 20°C during midday and early afternoon hours.** Hourly readings climbed steadily from morning lows near 12–14°C to the afternoon high before cooling into the evening, consistent with partly cloudy conditions, light southwesterly winds, and stable high pressure around 1018–1019 hPa. This outcome aligns with official monitoring agency records and multiple forecast models that converged on a high near 20°C (67–69°F). The market-implied odds reflect real-time aggregation of trader assessments backed by capital, incorporating the full day’s data as resolution approaches. Realistic challenges remain limited but could include minor discrepancies from station-specific measurements, post-hoc data revisions, or differences in how the exact maximum is officially tabulated.