Recent National Weather Service guidance and ensemble model runs point to an overnight low in the upper 70s to low 80s for Houston on August 21, reflecting the absence of any significant cold front or drier air mass to enhance radiational cooling. Typical August climatology shows mean lows near 77–78 °F, but persistent Gulf moisture, light winds, and urban heat retention often limit drops below 80 °F. The closely bunched probabilities across the 74–83 °F buckets capture uncertainty in cloud cover, dew-point depression, and the timing of any sea-breeze influence. Traders weigh these variables against historical analogs that rarely produce sub-75 °F readings this late in summer, keeping lower outcomes thinly traded.