Recent National Weather Service guidance and ensemble model runs indicate Chicago overnight lows near 60–65°F for August 24, consistent with late-summer climatology and Lake Michigan moderation. Trader sentiment clusters around the 56–59°F bins because small differences in radiative cooling—driven by cloud cover, near-surface wind speeds, and dew-point depression—can shift the minimum by several degrees. Clear, calm conditions promote stronger nocturnal heat loss and lower readings, while increased moisture or light mixing limits cooling. With resolution hinging on the official O’Hare observation, markets price in typical forecast spread from the 48-hour window, where model consensus remains moderate but sensitive to any last-minute high-pressure or frontal adjustments.