Highest temperature in London on July 4?

Platform comparison

Market context

The 0% crowd-implied probability for a high temperature exceeding the settlement threshold on 4 July 2026 at London City Airport reflects today’s cool, stable conditions: current readings show 13°C with 88% humidity and a gentle southerly breeze, far from the heat required to trigger a YES outcome[2][5]. This aligns with the Met Office forecast for Saturday, which caps the maximum at 15°C, confirming that no extreme heat event is unfolding in the immediate window[3].

Historically, July in London averages 23°C, yet heatwaves regularly push temperatures above 30°C, with Heathrow recording a record 40.2°C in July 2022[7]. While 2026 is projected to include at least one sustained scorcher above 30°C, today’s cool start and lack of atmospheric build-up suggest the threshold is unlikely to be breached on this specific date[7]. Traders should monitor the Met Office’s daily 12:00 UTC update for any sudden shifts in cloud cover or wind direction that could accelerate warming, as afternoon thunderstorms between 15:00–17:00 often follow rapid humidity spikes[7]. No major weather announcements are scheduled today, but the absence of high-pressure systems currently limits the potential for extreme heat[3].

Sources: 1 · 2 · 3 · 4 · 5

Methodology

This page is a comparison snapshot: one live quote, four reference venues with their key attributes, and a single execution path — every trade button routes to Prediction Today, which mirrors the Polymarket order book directly.

Resolution & payout

Polymarket-based markets settle through the UMA Optimistic Oracle on Polygon. A proposer submits the outcome, a two-hour challenge window opens, and unchallenged proposals finalise the resolution. Payouts settle automatically in USDC the moment the result is final — no bookmaker, no delay.

Kalshi-based markets settle in USD via the CFTC-regulated clearinghouse. Betfair Exchange settles in GBP/EUR net of commission. Manifold is play-money and does not pay out real funds.

FAQ

How does resolution work?

Through the UMA Optimistic Oracle on Polygon: a proposer submits the outcome, a two-hour challenge window opens, and USDC payouts settle automatically once the result is final.

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 Prediction Today 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.