Forecast models from Brazil’s National Institute of Meteorology (INMET) and major numerical weather prediction ensembles currently converge on a daytime maximum of 17–18°C for São Paulo on August 10, driven by persistent cloud cover, south-easterly flow, and the absence of strong subtropical high-pressure ridging that normally supports seasonal highs near 23–25°C. Recent runs show slightly cooler guidance than earlier in the week, reflecting increased moisture and reduced insolation that has lowered trader-implied probabilities for outcomes above 19°C while concentrating volume around 17–18°C. These temperatures align with observed cooling trends over the prior 48 hours and sit below August climatological averages, though minor model spread in boundary-layer mixing and timing of any weak frontal passage keeps a narrow window for 19°C still viable. Updated INMET briefings and 12–18-hour forecast revisions expected overnight remain the key near-term catalysts.