Marine layer development and Pacific high-pressure patterns are the dominant factors keeping San Francisco's June 15 high temperature forecast tightly clustered between 68–73 °F. Official National Weather Service guidance and ensemble models currently favor a modest warming trend from today's near-70 °F readings, tempered by persistent onshore flow and possible coastal stratus that limit afternoon insolation. Historical June climatology shows average highs near 68–70 °F, with marine influence creating a narrow daily range; slight variations in wind speed or boundary-layer mixing can shift the peak by 2–4 °F. Traders are weighting the 70–73 °F bins most heavily because recent model runs show limited divergence, while cooler or warmer outliers remain low-probability unless a stronger offshore flow develops overnight. Updated NWS forecasts and morning soundings tomorrow will provide the final inputs for market resolution.