Highest temperature in London on July 19?

Platform comparison

Market context

London City Airport recorded its peak temperature for 19 July 2026 at 21°C, a figure that has already locked the market outcome. On Polymarket, this contract trades entirely in USDC on the Polygon network, where conditional tokens now reflect a 100% probability for the 21°C range and 0% for all other brackets. The crowd-implied 0% YES probability for any alternative outcome aligns with the official Wunderground record, which lists this as the day’s highest reading for the EGLC station.

Historical July peaks at London City Airport typically cluster between 18°C and 24°C, with 21°C falling squarely within the median range for mid-month heat. In recent years, similar temperatures have occurred during stable, high-pressure spells without extreme heatwave conditions, making 21°C a statistically probable ceiling rather than an outlier. The current pricing reflects this baseline expectation, with no speculative premium for unseasonal spikes.

Traders should monitor the Met Office’s daily UK weather summaries and Wunderground’s hourly archives for any late data corrections, though settlement is fixed by the 12:00Z cutoff on 19 July. No further catalysts remain active; the resolution source is already finalised, and the on-chain market will settle automatically once the oracle confirms the 21°C reading. With the outcome determined, liquidity has evaporated, and conditional token positions are effectively locked until settlement.

Sources: 1

Methodology

This page reviews Highest temperature in London on July 19? 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

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

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.

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 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.

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.