**Coastal moderation from persistent marine layer and onshore flow is the dominant factor anchoring trader expectations for San Francisco’s August 3 high temperature in the mid-70s.** Official National Weather Service and AccuWeather guidance point to mostly sunny conditions with highs near 73–77 °F, consistent with the market’s top bins (76–77 °F at 36 %, 74–75 °F at 23 %, 78–79 °F at 19.5 %). A broader inland heat wave driven by westward-shifting high pressure has raised temperatures across the interior Bay Area and Central Valley, yet the sea breeze and cool Pacific waters continue to limit warming right at the coast, keeping San Francisco well below the seasonal extremes seen farther east. Recent model consensus shows only modest day-to-day variability through the first week of August, with no significant forecast shifts in the past 48 hours that would push probabilities toward the higher (80 °F+) or lower (≤73 °F) tails. Historical August climatology (average high ~68–70 °F) and the current weak-to-moderate warming signal together explain why traders have concentrated implied probability in the narrow 74–79 °F window while assigning very low odds to outliers.