Trade: Highest temperature in London on May 17?

Market context

On 17 May 2026, the highest temperature recorded at London City Airport will determine which range this market settles into. The settlement uses Wunderground's historical weather data for that specific station, with the window closing at midday UTC. The current order book on Polymarket implies just 1% probability for the YES outcome, reflecting the market's assessment of the likelihood of an exceptionally high temperature on that date.

London's May temperatures typically range between 15–22°C, with historical records showing that days exceeding 25°C occur occasionally but remain uncommon for mid-May. The Met Office's 30-year climate averages for London show a mean maximum of around 19°C in May, with extreme highs in the low-to-mid 20s representing roughly the 90th percentile. The 1% implied probability suggests traders are pricing in a scenario well beyond typical May conditions—likely requiring either an unusually early heatwave or an exceptional weather system.

Traders should monitor seasonal weather forecasts from the Met Office and European weather models as May 2026 approaches, particularly any signals of high-pressure systems or southerly airflow that could drive temperatures significantly above the May norm. The UK's climate patterns, including the influence of Atlantic systems and occasional continental warming events, create the baseline conditions against which such an outcome would be assessed. Current pricing reflects the statistical rarity of such an event occurring on any given May day in London.

Resolution source

This market settles from the official outcome published at https://www.wunderground.com/history/daily/gb/london/EGLC. 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 "Highest temperature in London on May 17?" 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?

$627 in lifetime turnover and $16K of resting liquidity puts this market in the below the median by volume for weather contracts on PolyGram. Order-book depth is modest — expect a couple of cents of slippage on $1k+ trades.

Last 24 hours alone saw $627 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.

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