**Persistent subtropical warmth and high humidity are anchoring Miami's overnight low near 79–81°F for August 18, aligning with the market's heaviest probabilities on the 80–81°F (46.5%) and 78–79°F (31.0%) bins.** Official guidance from the National Weather Service and extended forecasts (AccuWeather, timeanddate) show a continuation of the current warm, moist air mass with dew points in the mid- to upper-70s°F, limiting radiational cooling despite mostly clear skies. Light southeast winds and the urban heat island effect further suppress temperature drops, keeping the expected minimum close to or slightly above the long-term August average low of ~78°F. Recent nights have bottomed out at 80–82°F under similar conditions, reinforcing trader confidence in the upper-70s to low-80s range. No significant frontal passages or increased cloud cover are indicated in the next 24–48 hours that would drive cooler readings. Resolution hinges on the official Miami International Airport observation; any unexpected increase in low-level moisture or wind could nudge the low slightly higher, while stronger radiational cooling under perfectly clear, calm conditions remains the main path to the 76–77°F tier.