Recent National Weather Service and AccuWeather guidance shows Miami overnight lows stabilizing near 79–81°F under subtropical high pressure, light easterly flow, and elevated humidity that limits radiational cooling. Typical August climatology supports this range, with historical minimums rarely dipping below 78°F absent a rare frontal passage. Short-term models indicate minimal overnight cloud cover or precipitation on the 18th, keeping the diurnal temperature swing standard for the urban coastal environment. Trader consensus clusters on 80–81°F as the modal outcome because ensemble guidance shows little downside risk from unexpected cooling while urban heat retention caps further drops. Updated NHC and local office briefings through the evening of the 17th remain the key near-term inputs likely to refine probabilities.