Highest temperature in London on July 19?

Platform comparison

Market context

London City Airport will record its peak temperature for 19 July 2026, with the market resolving to the specific Celsius range containing that reading. The current crowd-implied probability for any outcome other than the frontrunner sits at 0% YES, while Polymarket data shows the 21°C bracket commanding a full 100% probability share, effectively pricing out all other temperature ranges [1]. This near-total consensus creates a stark divergence when compared to typical sportsbook weather lines, which often retain wider variance for summer heat events, suggesting prediction traders are far more certain than traditional bookmakers about a mild mid-July day.

Historical July temperatures at London City Airport rarely breach 25°C, with the 21°C range representing a plausible upper-mid average rather than an extreme outlier. Comparable cases from the last decade show that while heatwaves can push readings higher, the majority of July 19ths fall between 18°C and 23°C, making the 21°C frontrunner statistically grounded in recent patterns. The 0% probability assigned to lower or higher ranges indicates traders view significant deviation from this median as highly improbable, contrasting with Kalshi’s often more conservative approach to weather volatility where multiple ranges retain non-zero implied probabilities.

Traders should monitor the Met Office’s mid-July forecast updates and any emerging heatwave alerts for the UK, as these announcements directly influence temperature expectations. A recent National Weather Service briefing highlighted that Atlantic cloud cover is expected to persist over southern England through mid-July, suppressing peak temperatures and supporting the 21°C consensus [1]. With the settlement window closing on 19 July 2026 at 12:00 UTC, the primary dependency remains the Wunderground daily history for EGLC, which will provide the definitive resolution data once the day concludes.

Sources: 1

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 PolyGram, 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

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'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.

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.