**Clear skies and light winds overnight are enabling strong radiative cooling in Madrid, with forecasts converging on a minimum around 12–13°C for August 28, 2026.** Multiple models (including GFS-based and European guidance) project early-morning lows near 12–13°C under mostly clear conditions, consistent with the market’s tight clustering at 12°C (51%), 11°C (46%), and 13°C (46%). Recent days have already trended cooler than seasonal norms—the August 27 minimum reached 16.3°C, below the 1991–2020 average low of ~18°C—due to a stable high-pressure setup suppressing cloud cover and moisture. Key differentiating factors include subtle variations in boundary-layer humidity (dew points near 8–10°C), wind speeds (generally 2–4 m/s from the southwest or west), and exact timing of the coldest air pooling in the urban basin at ~650 m elevation. These elements determine how far nocturnal longwave radiation can drop temperatures before sunrise. Historical precedent shows August 28 minima rarely fall below 12–13°C, with the all-time record at 12.3°C (1956), reinforcing why sub-10°C outcomes carry low implied probability (7%). Traders appear to be weighting the consensus of official and ensemble forecasts against the possibility of slightly stronger cooling if winds remain lighter than expected. Resolution hinges on the official AEMET or equivalent station reading for the calendar day’s minimum.