Marine layer persistence and onshore flow from the Pacific are the primary drivers capping coastal Los Angeles highs near 80–81°F for August 19, aligning with the market’s leading 48.5% implied probability on that bin and 26% on 78–79°F. National Weather Service guidance and recent model runs indicate persistent low stratus and moderate marine influence suppressing afternoon temperatures below typical late-summer peaks, while historical August baselines for downtown and airport stations average 82–85°F under clearer conditions. Any overnight clearing or slight offshore shift could allow modest warming into the low 80s, though current ensemble consensus favors continued moderation. Updated National Weather Service and NOAA short-range forecasts expected later today will provide the next key data point for traders assessing resolution around the official downtown or airport maximum.