Recent numerical weather prediction models from sources including INMET and international ensembles project São Paulo maximum temperatures near 29–32°C on August 19 under stable high-pressure subsidence, clear skies, and light winds typical of late Southern Hemisphere winter. These conditions suppress cloud formation and allow strong daytime solar heating over the urban heat island, pushing readings above the 23–25°C climatological average. Minor model spread in boundary-layer moisture and afternoon mixing accounts for the tight clustering of market-implied probabilities around 29–33°C, with lower odds on extremes reflecting low precipitation risk and limited variability in steering patterns. Official station observations tomorrow will resolve the market.