**Donald Trump’s Truth Social posting volume during the September 15–22, 2026 window is shaped primarily by his established September cadence, which has run lighter than his 2026 annual average of roughly 19 posts per day.** September has historically tracked near 14 posts per day since he returned to office, producing a seven-day total centered in the 98–115 range and positioning the 100–119 bracket as the clear leader at 54.5% implied probability. The prior week (September 11–18) resolved in the 80–99 bracket, underscoring the month’s subdued pace. Traders have priced the 80–99 outcome at 29.1% to account for potential further moderation, while higher brackets (120–139 at 4.0%, 140–159 at 9.3%) remain discounted absent major escalations. Overlapping political catalysts—including UN General Assembly meetings, bilateral diplomacy, midterm election endorsements, and policy commentary on tariffs, AI, and media access—have sustained steady but not elevated output consistent with the September pattern. The market reflects trader consensus on this historical monthly rhythm rather than any late-week surge.