Recent National Weather Service and AccuWeather guidance points to an overnight low in the mid-to-upper 50s for San Francisco on August 25, driven by persistent onshore marine flow and a strengthening coastal inversion that limits daytime heating carryover. This aligns with climatological August averages near 57°F while reflecting a brief cooling trend that began earlier in the week, with forecast lows of 56–60°F across model runs. The 58–59°F bin leads market-implied odds at 48 percent because ensembles show minimal deviation from these values absent an unexpected offshore wind shift. Traders weigh the high likelihood of fog and stratus moderating temperatures against the slim chance of clearer skies pushing readings into the low 60s. Updated model runs and official briefings through the evening will provide the final inputs before resolution.