Highest temperature in London on July 12?

Platform comparison

Market context

The market bets on the peak Celsius reading at London City Airport for 12 July 2026, with the current crowd-implied probability sitting at 0% for any specific outcome. Today’s actual high is 29°C, but the settlement window closes at noon UTC, meaning the final recorded maximum must be captured before that deadline [6]. Programmatic traders should script a polling bot against the Wunderground history API to ingest minute-by-minute METAR data, filtering for the highest value before the 12:00Z cutoff to automate position adjustments.

Historical July peaks at EGLC typically range between 26°C and 35°C, with the average high around 22°C (72°F) [2]. Recent heatwave activity near 35°C on 9 July has elevated baseline expectations, yet cooling signals including potential thunderstorms suggest a dip is likely [4]. The 0% probability implies the market currently sees no viable range as a frontrunner, possibly due to the narrow settlement window or conflicting short-term forecasts, mirroring the volatility seen in the adjacent 13 July market where 27°C holds 39% [4].

Traders must monitor the Met Office 7-day forecast for London City Airport, specifically watching for sudden wind shifts or precipitation warnings that could cap the temperature before noon [3]. The primary dependency is the Wunderground daily history update, which resolves the market; any delay in this data feed could stall settlement. A recent BBC forecast notes sunny intervals and a moderate breeze for today, with a high of 83°F (28.3°C), providing a tangible baseline for algorithmic models to test against real-time sensor feeds [7].

Sources: 1 · 2 · 3 · 4 · 5

Methodology

Methodologically we separate two layers: the live probability (Polymarket mid-price) and the platform attributes (fee, KYC, settlement currency, payment rails). That keeps the comparison honest — a single canonical probability across the row, with the venue-by-venue trade-offs spelt out in the columns next to it.

Resolution & payout

At resolution the UMA oracle takes over: a proposer posts the outcome with a bond, any token holder can dispute within two hours. Without dispute the result is accepted and the smart contract distributes USDC instantly.

On Kalshi (CFTC-regulated) resolution runs through their in-house clearing engine in USD. Betfair Exchange settles after match end in the account's local currency. Manifold pays no cash — only its in-platform "mana" currency.

FAQ

Where can I trade this market with the lowest fees?

Polymarket is geo-blocked in the US/UK/EU. The easiest 0%-fee broker into the same order book is Polymarket Review UK. Kalshi charges up to 7% per trade; Betfair Exchange takes 2-5% commission on net winnings.

Is this market available outside the US?

Polymarket itself is geo-blocked in the US/UK/EU. Always check the legal status of prediction markets in your jurisdiction before trading.

What does Polymarket cost to trade?

Polymarket itself charges 0% — the only cost is the Polygon network fee, typically under $0.01 per transaction. Off-chain venues like Kalshi or Betfair charge 2-7% commission.

How fast are USDC deposits?

Polygon credits deposits after 12 confirmations — usually under 30 seconds. Withdrawals follow the same path and land back in your wallet within minutes.

How reliable are the quoted odds?

The YES/NO percentages are the live mid-prices of the Polymarket order book. On deep markets they move every few seconds; on thinner ones you'll see short plateaus.