This market trades on whether Shanghai's lowest temperature on May 17, 2026 will be exactly 21°C. The outcome is definitively resolvable through official weather data from China's meteorological authorities, which record the daily low temperature to one decimal place with high precision. The current YES odds of 0% reflect extreme trader skepticism that the low will hit this specific temperature. In May, Shanghai typically experiences lows in the 18–23°C range due to its subtropical climate and transition into early summer conditions, making 21°C meteorologically plausible—yet exact-temperature markets are inherently difficult to predict because they require precision to within 0.5°C. Weather systems, cloud cover, wind patterns, and overnight humidity all influence the final low. The market has seen minimal volume at $753 in 24 hours despite reasonable liquidity of $11,288, suggesting traders view this outcome as sufficiently improbable that it doesn't warrant significant position-building. The extreme price assignment implies either that current atmospheric conditions are expected to produce a cooler or warmer low than 21°C, or that the fundamental difficulty of exact-temperature prediction keeps participation low regardless of the specific target.
What factors could move this market?
Shanghai's climate in mid-May represents a transitional period between spring and early summer, with gradually increasing temperatures and humidity. Historical meteorological data shows that May lows in Shanghai typically range from 18 to 24°C, though the exact daily minimum depends on multiple interconnected factors including overnight cloud cover, wind speed and direction, residual daytime heat retention, and atmospheric moisture levels. A low of exactly 21°C sits near the median of this historical range, making it meteorologically plausible from a climatological perspective—yet the market's 0% odds suggest that traders collectively believe actual conditions will deviate from this specific threshold.
Exact-temperature prediction markets face a fundamental inherent challenge that distinguishes them from broader directional markets. Even a small shift in weather patterns—a passing cold front, unexpected cloud clearance, or wind shift—can push the low to 20.8°C or 21.2°C, causing the market to resolve NO despite being meteorologically close to the target. Traders pricing this market at 0% may be betting on one of several scenarios: (1) a cooler low in the 18–20°C range due to an approaching weather system or unexpected clear skies allowing radiative cooling, (2) a warmer low above 22°C from retained daytime heat or persistent cloud cover, or (3) simply recognizing that the precision required makes exact-temperature markets inherently difficult to time and capitalize on.
Recent weather trends in Shanghai have shown variable spring conditions, with some warm days followed by cooler nights as different air masses move through the region. The current price assignment—near-total zero—implies extreme confidence in deviation, reflecting both the mathematical difficulty of exact-temperature prediction and market participants' real-time assessment of atmospheric conditions developing toward May 17. The May transition period typically brings moderate swings in the daily low, with cold air intrusions occasionally producing lows in the 18–20°C range and warm systems keeping lows above 22°C. May 17 represents a specific transitional day in Shanghai's seasonal calendar, and forecasters typically issue official lows for such dates with moderate rather than high confidence.
The market's low volume ($753 in 24 hours) paired with reasonable liquidity ($11,288) suggests speculative trading interest is minimal, though the market remains open for any traders who wish to take contrarian positions against the consensus zero-probability pricing. The stakes of this market hinge entirely on precision: a measurement of 21.0°C resolves YES, while 20.9°C or 21.1°C both resolve NO. Verification will rely on official data from Shanghai Pudong International Airport meteorological station or the China Meteorological Administration's published records, both of which provide definitive daily temperature measurements to one decimal place, used for market resolution.
What are traders watching for?
Shanghai official meteorological low reading on May 17 — must equal exactly 21.0°C (or 21°C) to resolve YES.
China Meteorological Administration official daily records — the authoritative resolution data source for Shanghai's daily temperature minimums.
Overnight weather system development — any passing cold front, cloud cover shifts, or wind changes may alter the final low.
Pre-market forecasts on May 16 — meteorologists' evening low forecast for May 17 will influence final trader positions.
How does this market resolve?
The market resolves YES if Shanghai's official lowest temperature on May 17, 2026 is exactly 21°C according to China's meteorological authorities. It resolves NO if the recorded low is any temperature other than 21°C.
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.
