This market narrows down San Francisco's daily high temperature to an extremely precise one-degree range on May 18, 2026. With current odds at 0%, traders are expressing very low conviction that the high will fall within exactly 64-65°F, suggesting they expect conditions to reach either above 65°F or below 64°F. San Francisco's late May weather typically ranges from the mid-50s to mid-60s across diverse microclimates—fog-heavy zones near the bay can be 5-10 degrees cooler than inland areas—making 64-65°F a plausible but narrow target band. The resolution will depend on the official daily high reported by NOAA or the local National Weather Service office. The extreme consensus against this range (0% YES) reflects the inherent difficulty of forecasting precise daily temperatures. Even professional meteorologists typically forecast ranges rather than exact single-degree bands several days in advance. This tight prediction market reflects both the precision required and trader skepticism about hitting such a narrow window reliably, especially when small shifts in fog patterns or thermal timing can shift the actual high by several degrees.
What factors could move this market?
San Francisco's climate in mid-May is characterized by cool, temperate conditions heavily influenced by coastal maritime air masses and the moderating effect of the Pacific Ocean. Historically, the city's average daily high in May ranges from 62-68°F depending on the week, with considerable day-to-day variability driven by fog patterns and atmospheric setup. A high of 64-65°F sits squarely within typical late-May conditions—neither unusually warm nor exceptionally cool for the season. The city's complex topography creates significant microclimatic variation: neighborhoods immediately adjacent to the bay experience stronger marine layer influence and cooler conditions, sometimes 5-10 degrees Fahrenheit cooler than inland areas just a few miles away. May is a transitional month when the marine layer begins its annual weakening pattern, but breakthrough days with highs in the 75-85°F range remain possible when inland systems suppress the protective fog layer. Trading markets for such specific temperature ranges must account for the compounding forecasting uncertainty inherent in meteorology: even highly skilled meteorologists typically have error margins of ±3-5°F on temperature predictions several days in advance, and day-to-day variability in marine layer strength can shift outcomes by that magnitude. The current 0% YES odds suggest traders believe the actual May 18 high will diverge from the 64-65°F band—either exceeding 65°F from a warming pattern that suppresses morning fog, or falling below 64°F from a cooler system or persistent marine layer. Historical analysis of May 18 dates in prior years provides reference points, though climate variability and long-term warming trends complicate direct comparison. Key atmospheric drivers on May 18 will include the position and strength of the Pacific high-pressure system, proximity of any approaching cold fronts, timing of morning fog burn-off, and afternoon wind patterns. Traders monitoring real-time National Weather Service forecasts, NOAA satellite data, and local weather station reports will refine expectations as May 18 approaches. The extreme consensus against this range reflects rational skepticism about such precision in daily forecasting.
What are traders watching for?
NOAA official daily high temperature report for San Francisco on May 18, 2026—the exact resolution data point used for settlement
National Weather Service updated forecasts May 17-18: each refresh will tighten the predicted range as the date approaches and models converge
Morning marine layer persistence on May 18: strength and timing of fog burn-off directly determines whether high stays below 64°F or exceeds it
Upper-level atmospheric pattern: any weak low-pressure system or high-pressure ridge position shift on May 18 impacts inland warming potential
How does this market resolve?
Market resolves YES if the official daily high temperature for San Francisco on May 18, 2026 is between 64°F and 65°F inclusive, as reported by NOAA or the National Weather Service. Otherwise it resolves NO.
Polymarket Trade is an independent third-party interface to the Polymarket CLOB prediction market exchange on Polygon — not affiliated with Polymarket, Inc. Prediction markets aggregate trader expectations into real-time probability estimates. Every market question resolves YES or NO based on a specific event outcome; traders buy shares of the side they believe will resolve positively. Prices range 0¢ (certain no) to 100¢ (certain yes) and naturally reflect the crowd-implied probability of YES. Polymarket Trade is non-custodial — your funds never leave your wallet. Open the full interactive page linked above to place orders, see order book depth, and execute a trade.
