Highest temperature in London on July 4?

Platform comparison

Market context

The highest temperature recorded at London City Airport on 4 July 2026 will determine the outcome of this weather contract, with the market currently pricing a 28°C peak at 80% and 29°C at 20%[1]. On Polymarket, this conditional token trades on the Polygon network using USDC, where the crowd-implied probability for any outcome below 28°C sits at 0%, reflecting a strong consensus that the day will be warm[1]. The settlement window closes at 12:00 UTC on 4 July 2026, once Wunderground publishes the first official data point for the day[1].

Historically, July is the hottest month at London City Airport, with an average high of 72°F (22°C), though recent extremes have pushed temperatures significantly higher[4]. The UK experienced a brief but intense heatwave in mid-July 2025, where new temperature records were evaluated and verified across the British Isles[9]. While the absolute highest temperature ever observed in London reached 40.2°C at Heathrow in 2022, the current market pricing suggests a more moderate, yet still warm, peak for this specific date[6].

Traders should monitor the Met Office daily forecast for London City Airport, which currently indicates a maximum feels-like temperature of 25°C with a daily highest gust of 27mph[5]. The immediate catalyst is the real-time weather progression, as southerly winds and 88% humidity observed tonight could influence the afternoon peak[2]. With only two days remaining until resolution and thin volume, the contract remains volatile, making the official Wunderground data release the critical dependency for settlement[10].

Sources: 1 · 2 · 3 · 4 · 5

Methodology

This page reviews Highest temperature in London on July 4? across five venues. The live probability is the Polymarket mid-price, sourced directly from the on-chain Polygon order book; the comparison columns benchmark each venue on fee structure, KYC, settlement currency and payment rails. Every CTA routes to Kalshi UK, which mirrors the Polymarket order book at 0% fees.

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 Kalshi UK. Kalshi charges up to 7% per trade; Betfair Exchange takes 2-5% commission on net winnings.

What's the difference between YES and NO shares?

A YES share pays $1.00 if the event happens, $0 otherwise. A NO share pays $1.00 if the event doesn't happen. The market price between 0¢ and 100¢ is the implied probability.

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.

Do I need to KYC for this market?

On Polymarket directly, no — it's wallet-based. Intermediary brokers like Kalshi UK trigger KYC only above $1,500 of lifetime trading volume; under that you trade pseudonymously with a single wallet address.

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.