Forecast uncertainty in overnight radiative cooling and boundary-layer mixing drives the closely matched Polymarket odds for Austin’s August 29 minimum temperature. Current National Weather Service guidance points to clear skies, light southerly winds, and dew points in the mid-70s, supporting a most-likely low near 76–78 °F—within the historical late-August average of 72–75 °F at Austin-Bergstrom. Subtle differences in model handling of urban heat-island retention versus enhanced mixing from any weak southeasterly flow can shift the realized minimum across the 72–81 °F range, while rare scenarios of stronger advection or unexpected cloud cover explain the smaller but notable probabilities attached to extremes above 86 °F or below 67 °F. Updated model runs and evening observations ahead of the overnight period remain the key near-term catalysts.