Highest temperature in London on July 31?

Platform comparison

Market context

The relevant event is the day’s peak temperature at London City Airport, and the contract settles on the range containing that single highest reading from the Wunderground history page. London can get very warm in late July, but the venue matters: airport stations often differ from central London sites, so a forecast for the city centre is not always a clean read-through for EGLC itself.

A 0% implied YES price suggests the market is already treating the required range as effectively out of reach. That is consistent with London’s recent upper-end summer history: Heathrow reached 37.8°C on 31 July 2020, while Kew Gardens hit 37.3°C the same day, and Heathrow also logged 37.8°C in one of the city’s most extreme recent July heat episodes.[1][4][6] More broadly, London’s all-time maximum is 40.2°C, recorded at Heathrow and St James’s Park during the 2022 heatwave, which shows the ceiling for an exceptional summer setup, even if it does not imply anything about today’s observation window.[8][12]

Traders should watch the UK Met Office short-range forecast and any live London heat updates for whether the afternoon warms enough to challenge the upper-20s or low-30s Celsius marks seen in recent warm spells.[3][10][13] For a contract settled in USDC, the main on-chain angle is timing: price can stay pinned at zero until the London City Airport observation is finalised, then any payout risk is determined by the Wunderground maximum for the full calendar day rather than intraday headlines. Macro crypto conditions can still matter at the margin through BTC and ETH volatility, but for a weather binary the dominant driver is the temperature print itself, not funding or whale flows.

Sources: 1 · 2 · 3 · 4 · 5

Methodology

Methodologically this overview focuses on on-chain pricing: Polymarket's live mid comes from the Polygon conditional-token order book and settles automatically in USDC. The other three venues — Kalshi, Betfair, Manifold — sit alongside as off-chain reference points so you can see how the contract translates across regulatory and settlement regimes.

Resolution & payout

Settlement is on-chain via UMA Optimistic Oracle. A proposer posts the outcome with a bond, a two-hour dispute window opens, then the smart contract lifts winning conditional tokens to 1 USDC and sends payments to holders' wallets automatically. No withdrawal fees beyond Polygon gas.

Off-chain venues (Kalshi, Betfair, Smarkets) settle in local fiat through bank-side clearing — faster than SWIFT, slower than on-chain. Manifold pays no real cash.

FAQ

What are crypto prediction markets?

Crypto prediction markets are on-chain smart contracts where you buy YES or NO shares on a future crypto event (e.g. "BTC above $100k by year-end"). The market price between 0¢ and 100¢ is the implied probability.

Why USDC and not ETH or USDT?

USDC is the Polygon standard — audited reserves (Circle, monthly attestation), deepest order book, low gas costs. ETH volatility would distort probability quotes; USDT has thinner Polygon liquidity than USDC.

How does UMA secure the resolution?

The UMA Optimistic Oracle uses a bond system: a proposer posts a bond, a two-hour challenge window opens. On dispute the losing side forfeits the bond — financial incentive for honest resolution.

How volatile are crypto prediction markets?

Crypto markets react to spot prices — a 5% BTC move typically shifts a "BTC above X by date" market 10-20%. Polymarket crypto market liquidity is usually six-figure USD, sufficient for active trading.

Are crypto prediction markets taxable in the US?

In the US, prediction market gains are typically treated as ordinary income or short-term capital gains depending on holding period. Consult a tax professional for your specific situation — we cannot provide tax advice.