Forecast models from the National Weather Service and private sources project an overnight low near 77°F for Austin on September 17, driven by southeasterly flow maintaining elevated boundary-layer moisture and limiting radiative cooling under partly to mostly cloudy skies. A slight afternoon thunderstorm chance could further reduce nighttime temperature drops by enhancing cloud cover and downwelling longwave radiation. Trader sentiment clusters tightly across the 72–77°F buckets because ensemble guidance shows modest spread in low-level humidity and wind speed, with historical September minima in the mid-70s providing context. Updated model runs and official forecasts ahead of the 48-hour window remain the key near-term catalysts for any shifts in implied probabilities.