94% Yield: Dallas Max Temperature Settlement Arbitrage Hits Kalshi and Polymarket

A structural settlement lag between Polymarket and Kalshi has opened up a massive synthetic arbitrage window on May 31 weather contracts. Because the actual weather data for May 31 is already finalized but Kalshi contracts do not officially expire until June 7, mispriced books on both platforms allow traders to lock in significant spreads. ### The Setup The top opportunity is in the Dallas May 31 temperature markets. Polymarket's "92°F or higher (NO)" contract is trading at 0.1¢ (implying a 99.9% probability that the temp was 92°F or higher). Meanwhile, Kalshi's "92° or below (YES)" contract is trading at 1.0¢. By buying Polymarket NO at 0.1¢ and Kalshi YES at 1.0¢, you are holding opposing sides of the exact same event boundary. Balancing your size 10:1 (Kalshi to Poly) yields a net return of 9,423.81% on capital once settlement finalized. A $500 total position split accordingly returning $47,119. ### Liquidity & Execution Constraints Before executing, check the order book depth. While the theoretical returns are extreme, actual execution limits are dictated by Kalshi's thin books on specific contracts: * **Dallas & Denver:** Kalshi volume is exceptionally thin ($3,462 and $3,668 respectively). Large block orders will suffer heavy slippage. Limit orders are mandatory here. * **Los Angeles & Seattle:** These present the cleanest execution pathways. Los Angeles has robust two-sided liquidity with $41.2k on Poly and $43.8k on Kalshi. Seattle is similarly liquid with over $60k Poly volume and $15.8k on Kalshi.