Forecast consensus from the National Weather Service and local models points to a maximum temperature near 80–82°F in Seattle on August 20, aligning with the market’s tight clustering around the 82–83°F and 80–81°F bins. Marine air influence and onshore flow from the Pacific moderate daytime heating despite a warmer-than-average summer baseline, while light winds and limited cloud cover allow modest afternoon warming. Model spreads and micro-scale variations in the Puget Sound region create the narrow probability gaps between these outcomes, with any late-day sea breeze shift or slight timing difference in peak insolation able to tip the daily high by 1–2°F. Updated NWS guidance later today will refine the final range ahead of resolution.