NFL-driven prediction-market activity surged in September 2026, with Kalshi recording $4.89 billion in weekend volume and an all-time daily record of $2.433 billion on Sunday. Across eight platforms, Sunday volume reached $3.12 billion after $3.17 billion on Saturday. Polymarket’s NFL contracts rose 4,399% week over week globally to $27.62 million during Sept. 7-13, while its US platform rose 1,760% to $23.20 million; Polymarket reached 43.8% of Kalshi’s football volume within months of launching its CFTC-regulated US arm. The platforms’ reported totals cover different scopes and periods, including approximately $14.1 billion in combined sports volume in one September week and $9.33 billion over a separate 30-day period.