Recent atmospheric patterns over southeastern Brazil, including a strengthening high-pressure system and southerly flow, are keeping maximum temperatures in São Paulo near seasonal norms for mid-May. Ensemble forecasts from global models show daytime highs most likely settling between 19°C and 21°C, as increased cloud cover and light showers limit solar heating while dew points remain moderate. These conditions align with historical May climatology, where average highs hover around 22°C but often dip under frontal influences. Traders appear to weigh the narrow spread in guidance against the chance of clearer skies pushing readings to 22°C or a stronger cool-air advection holding them at 19°C, with resolution depending on the final National Institute of Meteorology analysis at 18:00 local time on May 18.