Cloud cover and light rain showers associated with a passing frontal system are capping daytime heating in Seattle on September 29, keeping the daily maximum in the low-to-mid 60s°F. Persistent marine layer moisture and southwesterly flow off the Pacific suppress surface warming by limiting solar insolation, while modest winds prevent strong mixing that could otherwise boost readings. Official guidance and recent model runs cluster around 60–63°F, aligning with the closely matched market-implied odds for the 60–61°F and 62–63°F bins. Historical September 29 averages near 66°F highlight how today’s conditions deviate from typical late-summer patterns, with any late-day clearing the main variable that could shift the peak within that narrow range.