Persistent summer heat and high humidity across southeast Texas keep overnight lows in Houston near or slightly above the long-term August average of 78°F, with National Weather Service guidance centering on 79–81°F for the night of August 21–22. Limited radiative cooling from muggy air masses, light winds, and scattered cloud cover or isolated showers prevents sharper drops, while the absence of any late-summer cold front or tropical influence maintains the warm baseline. Small forecast differences in timing of any overnight convection or boundary-layer mixing create the tight clustering of market-implied odds between the 74–81°F buckets, as traders weigh model consensus on these marginal variables ahead of the final minimum reading.