**Clear skies and light northerly winds overnight are supporting radiational cooling toward the mid-to-upper 50s in Seattle on August 23, 2026.** Official forecasts from the National Weather Service and other sources project a low around 56–58 °F, consistent with the long-term average minimum of 56.3 °F for the date and recent August nights that have ranged from the mid-50s to near 60 °F. The balanced market prices on the 56–57 °F and 58–59 °F bins reflect modest differences across model guidance and measurement sites (e.g., Sea-Tac Airport versus urban stations), with traders weighting the expected overnight minimum under mostly clear conditions and dew points near 55 °F that limit further cooling. The 29.5 % on 53 °F or below captures residual uncertainty if winds remain lighter or if localized urban effects prove slightly cooler than guidance. No significant synoptic changes—such as marine intrusions, frontal passages, or cloud cover—are expected before sunrise to shift the outcome materially.