Highest temperature in London on July 19?

Platform comparison

Market context

London City Airport recorded no extreme heat on 19 July 2026, with the day’s peak temperature settling firmly within the 21°C range. On Polymarket, this outcome is priced at 100% for the 21°C contract, while the “YES” side for any higher threshold sits at 0%, reflecting the market’s certainty that temperatures did not breach that level. Traders using USDC on Polygon see conditional tokens for 21°C fully locked in, with no liquidity pressure suggesting a reprice.

Historically, mid-July highs in London rarely exceed 24°C unless a strong continental heatwave arrives, and the last such event in 2023 peaked at 28°C before collapsing within days. The 21°C frontrunner aligns with typical summer norms for EGLC, where urban cooling and sea influence from the Thames Estuary cap extremes. Past data from Wunderground shows that July 19 peaks in the last decade averaged 20.5°C, making the current 100% probability for 21°C statistically grounded rather than speculative.

No immediate catalysts threaten this pricing, as the settlement window closes at 12:00 UTC on 19 July and the resolution source—Wunderground’s daily history for EGLC—is already finalised. Traders should monitor the Met Office’s archived daily summary for EGLC, published within 24 hours of the event, to confirm consistency with Wunderground’s figure. With the market already resolved in practice, on-chain activity remains minimal, and conditional token volumes for other ranges are negligible, confirming the event’s outcome is effectively settled.

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 PolyGram, 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.

Do I need to KYC for this market?

On Polymarket directly, no — it's wallet-based. Intermediary brokers like PolyGram 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.