Recent forecasts from agencies like the UK Met Office and BBC Weather indicate Madrid's overnight minimum on August 21 will likely settle near 18–20°C, supporting the tight clustering of market-implied probabilities around those thresholds. Clear skies and light southwesterly winds under a stable high-pressure regime promote efficient nocturnal radiative cooling after daytime highs near 30°C, but limited cloud cover or slight increases in boundary-layer mixing could raise the low by 1–2°C. Madrid’s high-elevation continental setting amplifies diurnal temperature swings, with historical late-August averages around 18–19°C providing context for the narrow spread. Updated model runs tonight will refine exact minimum readings at official stations, where small variations in timing or local siting often decide between adjacent Celsius values.