Northwest winds and clear skies are driving trader focus toward overnight lows in the upper 50s to low 60s°F for Chicago on August 23, consistent with National Weather Service guidance showing a forecast low near 61°F under mostly clear conditions. Radiational cooling under high pressure, combined with cooler air advection from the northwest, supports these readings, which align closely with climatological norms for late August near Lake Michigan. Recent model consensus and surface observations indicate limited cloud cover overnight will enhance temperature drops, while lake moderation prevents deeper cooling. The elevated 45.5% implied probability on 51°F or below reflects uncertainty in exact minimum timing and microscale variations, though probabilities drop sharply above 64°F given the current steering pattern.