**A strengthening El Niño event, now forecast with >90% probability of becoming very strong through fall and winter 2026–27, is the dominant near-term driver shaping USDM D4 probabilities for early September.** Current conditions as of late August show D4 (the most severe category, typically <2nd percentile of historical moisture) limited primarily to portions of Idaho and scattered western and southern Plains/Rockies sites, with overall D1–D4 coverage near 47–48% of the contiguous US but D4 area only ~1.5–1.8%. NOAA’s September 2026 outlook favors above-normal precipitation across much of the western CONUS and southern tier due to El Niño composites and monsoon influences, supporting potential localized improvement or removal in the Southwest, while above-normal temperatures and drier signals favor persistence or modest expansion in the Pacific Northwest. These dynamics create tight differentiation among the closely matched leading outcomes (10+ states at 44.5%, 5–6 or 7–9 states at 38%), as D4 boundaries depend on precise precipitation deficits, soil moisture recovery, and USDM author delineation; rapid monsoon surges or frontal systems could shift state counts within days. The next USDM release and updated CPC monthly/seasonal outlooks will provide key resolution signals.