**Official forecasts from the National Weather Service and major models converge on an overnight low in the low 70s°F for Atlanta on August 21, 2026, reflecting moderate uncertainty in exact minimums that explains the tight clustering of leading market outcomes around 72–77°F.** Key drivers include expected partly cloudy skies with isolated evening thunderstorms (20–50% chance), which limit radiational cooling compared to clear conditions, and light winds (under 5–10 mph) that reduce mixing of cooler air. Dew points near 70–72°F support minimum temperatures close to those values, while Atlanta’s urban heat island effect adds a few degrees relative to rural baselines. Afternoon heating to the low 90s with high heat indices (near 100–103°F) sets up strong diurnal ranges, but any earlier or more persistent cloud cover from convective activity could raise the daily minimum by 1–3°F. Recent model runs show minor disagreements on storm timing and coverage, keeping probabilities split across the 72–77°F bins rather than concentrating on one outcome. Clearer skies after midnight favor the lower end of that range, while lingering moisture or thicker clouds support the higher side. Updated NWS guidance and short-range model ensembles will refine these details through the evening.