Traders see the 56–59°F bins as nearly even money because official National Weather Service model runs and ensemble guidance show Seattle’s minimum temperature on August 25 hovering right at the boundary between those two outcomes. Late-summer marine-layer stratus and variable onshore flow are limiting nocturnal radiative cooling, while any breaks in cloud cover or slight wind shifts could add or subtract a degree or two. With the forecast window now less than 24 hours away, small revisions in the 00Z or 12Z model cycles are the dominant near-term driver, keeping the two leading probabilities locked within 1 percentage point and leaving lower or higher bins as long-shot tails.