National Weather Service and NOAA model consensus points to a highest temperature in the mid-70s for Los Angeles on September 17, driven by persistent onshore flow and a strengthening marine layer that limits daytime heating under mostly sunny afternoon conditions. Recent observations show highs near 77–78°F, consistent with climatological norms of 76°F for mid-September at coastal stations, while reduced cloud cover and light southwest winds favor modest warming without pushing into the upper 70s. Traders assign the highest probability to the 76–77°F bin as forecast guidance shows limited variability across ensemble runs, though slight differences in marine layer depth or timing of clearing could shift the peak by a degree or two.