Upper-level ridging over the Southwest is driving an early-October heat wave across the Bay Area, compressing the marine layer and limiting onshore flow to produce above-normal overnight temperatures. Official NWS guidance and model consensus currently place San Francisco’s October 4 low in the low-to-mid 60s, well above the 1991–2020 average of 55.3 °F for the date. Variable marine-layer depth, light winds, and possible thin cloud cover remain the key uncertainties that could shift the minimum a few degrees in either direction. New model runs and evening forecast updates from the National Weather Service will provide the next clearest signals ahead of the overnight period.