**Marine layer persistence and onshore flow are the dominant controls on San Francisco’s June 14 maximum temperature.** Persistent June marine stratus and fog, reinforced by a moderate southwesterly to westerly breeze off the cool Pacific, limit daytime heating and keep the city well below inland values. Official guidance from the National Weather Service and local forecasts points to a high near 68–72 °F under partly to mostly sunny skies once any morning low clouds burn off, aligning with the market’s clustered probabilities around 70–73 °F. **Small differences among the leading bins (70–71 °F, 72–73 °F, 74–75 °F) hinge on the exact timing and depth of marine-layer clearing plus subtle variations in wind speed and direction.** Stronger or more prolonged onshore flow and a deeper marine layer suppress the high toward the lower end of that range; a quicker burn-off or lighter winds allow modest additional warming. Current model consensus and recent satellite trends show the stratus retreating during the day but reforming overnight, supporting the tight clustering rather than extremes. **Historical June averages near 66–68 °F and the absence of strong offshore flow or heat-wave advection keep the risk of readings above 76 °F or below 68 °F low.** Traders are therefore weighting the most probable outcomes based on these well-observed coastal dynamics rather than outlier scenarios.