**Persistent late-summer heat and southerly flow are keeping overnight lows elevated in Austin, with official forecasts centering the September 13 minimum in the upper 70s.** National Weather Service guidance and multiple model runs project a low near 77°F under partly cloudy skies, light south winds, and dew points in the low-to-mid 70s, consistent with the market’s top-weighted bins of 76–77°F (37.5%) and 78–79°F (29%). This warmth stems from a strong upper-level ridge suppressing cooler air intrusions and limiting nocturnal radiational cooling, a pattern that has produced above-normal lows throughout early September. Historical climatology shows an average low of ~69°F for the date, but current conditions reflect the ongoing heat dome, with heat-index values exceeding 105°F during the day and little relief at night. The tight clustering of probabilities around 76–79°F reflects model consensus on minimal day-to-day variability, while lower-probability tails (e.g., 72–73°F or 80–81°F) account for possible small shifts from wind changes, urban heat-island effects at the official Austin-Bergstrom measurement site, or minor forecast adjustments in the final hours. Resolution hinges on the verified daily minimum reported by the National Weather Service.