Trade: Lowest temperature in Shanghai on May 18?

Market context

Shanghai's lowest temperature on 18 May 2026 will be recorded at Pudong International Airport Station and settled against Wunderground historical data. The current order book on Polymarket implies a 23% probability for the YES outcome, reflecting trader expectations that the low will fall within a specific temperature range on that date. This probability is formed through continuous trading activity as participants weigh seasonal patterns, climate models, and their confidence in forecast accuracy.

May in Shanghai typically marks the transition into early summer, with daily lows averaging 17–19°C, though variability increases during this shoulder season. Historical data from previous May 18ths shows considerable year-to-year fluctuation; cold fronts occasionally push lows below 15°C, whilst warm, humid patterns can keep them above 20°C. The 23% implied probability suggests traders are pricing in a moderately unlikely outcome relative to typical May conditions, though the specific temperature threshold being wagered on will determine whether this reflects pessimism or optimism about cooler conditions.

Key variables affecting the outcome include upper-air pressure patterns developing in late April and early May, tropical cyclone activity in the western Pacific, and any cold air masses moving southeastward from higher latitudes. China's meteorological forecasts typically become more reliable 10–14 days before the settlement date. Traders should monitor seasonal climate outlooks from the China Meteorological Administration and watch for any significant weather systems forecast to affect the Yangtze River Delta region in mid-May, as these will shift market pricing closer to the settlement window.

Resolution source

This market settles from the official outcome published at https://www.wunderground.com/history/daily/cn/shanghai/ZSPD. A proposer submits the final result to the UMA optimistic oracle on Polygon; the two-hour dispute window closes and payouts clear in USDC.

How to trade this market step by step

The mechanics for trading "Lowest temperature in Shanghai on May 18?" are the same as any other PolyGram event contract. Each YES share resolves to $1 if the event happens, or $0 if it doesn't. The current price between 0¢ and 100¢ is the market's probability estimate, set live by the order book.

1. Sign in on polygram.ink with your email — no full KYC under $1,500 lifetime trading volume.
2. Deposit USDC on Polygon (lowest fees, ~$0.01 per transaction) or Ethereum. Funds credit after 12 confirmations.
3. Pick a side. Buy YES if you believe the event will happen; buy NO if you think it won't. The current YES price reflects the market's collective probability.
4. Size your position. If you stake 100 USDC at 50% YES, you'll receive shares that pay $200 if YES resolves true — a 100% gross return. If NO resolves, your shares are worth $0.
5. Set risk controls (optional). Stop-loss, take-profit, and limit-order types all supported. Use the trade ticket's slippage box to cap your maximum entry price.
6. Wait for resolution. When the event resolves on-chain via the UMA optimistic oracle, the winning side settles to 100¢ automatically and USDC hits your balance within seconds. Withdrawable to any wallet you control.

How active is this market?

$115 in lifetime turnover and $6K of resting liquidity puts this market in the below the median by volume for weather contracts on PolyGram. Order-book depth is thin — large orders may need to be split across the book or executed as limit orders.

Last 24 hours alone saw $115 in turnover, well above the lifetime daily-average for this market — a clear sign of news catalysing trader activity right now.

The market has been open for under a month — fresh enough that information asymmetry remains a real factor.

Higher-volume markets tend to have tighter spreads and faster price discovery — meaning the displayed YES/NO percentages are more likely to reflect the true crowd-implied probability rather than a single trader's directional view.

Key terms

YES / NO share

A binary outcome token that pays $1.00 if the underlying claim resolves true (YES) or false (NO), and $0 otherwise. The market price between 0¢ and 100¢ is the implied probability.

CLOB

Central limit order book. The matching engine that pairs YES buyers with NO buyers (effectively the same trade). Polymarket's CLOB on Polygon executes trades on-chain via the conditional-tokens framework.

Liquidity

USDC capital sitting in resting limit orders inside the order book. Deeper liquidity means smaller slippage on large trades and a tighter bid-ask spread.

UMA optimistic oracle

The on-chain dispute system that settles each Polymarket market. A proposer submits the outcome, a two-hour challenge window opens, and unchallenged proposals finalise the resolution.

Slippage

The difference between the displayed mid-price and your fill price. Affects market orders most; limit orders avoid slippage but may take time to fill.

Conditional token

ERC-1155 outcome share issued by Gnosis Conditional Tokens on Polygon. The token type that resolves to $1.00 or $0.00 at settlement.

See the full prediction-market glossary →

Frequently asked questions

Risk and regulatory note

Prediction-market positions can lose 100% of staked capital. Outcomes are uncertain by definition — historical accuracy of crowd-implied probabilities is high in aggregate but not for any single market. PolyGram does not provide investment advice. Trade only with capital you can afford to lose.

Regulatory status varies by jurisdiction. Germany, the United States, and most EU countries treat Polymarket-style event contracts under one of three frameworks: financial derivative, gambling product, or unregulated novel asset. Consult local counsel before trading.

Related prediction markets

Explore more prediction market odds and trading opportunities on PolyGram:

• All weather prediction markets
• How prediction markets work
• Browse all prediction markets on PolyGram
• Top prediction market traders
• Back to PolyGram home