Highest temperature in London on August 19?

Platform comparison

Market context

On 19 August 2026, the highest temperature recorded at London City Airport will determine which range this market settles into. The resolution hinges on the Daily Observations table from Weather Underground rather than summary figures, a distinction that occasionally produces material differences in recorded extremes. The current crowd-implied probability of 0% suggests traders are pricing in either exceptionally cool conditions or significant uncertainty about whether any specific temperature band will be hit.

London's August temperatures typically range between 20–26°C, with historical highs occasionally reaching 30°C or above during heat waves. The 2022 heatwave saw temperatures exceed 40°C across parts of the UK, though London City Airport recorded 35.9°C on 19 July that year. August tends to be slightly cooler than July, and the long-range outlook for summer 2026 remains uncertain; current seasonal models suggest near-normal conditions for the period, which would imply highs in the low-to-mid 20s Celsius. The 0% probability across all ranges suggests the market may be awaiting clearer weather forecasts or experiencing liquidity constraints rather than reflecting genuine consensus.

Traders should monitor the Met Office's extended forecast as August 2026 approaches, particularly any alerts for heat waves or unusual pressure systems. The UK's Atlantic weather patterns typically dominate August, making early-month forecasts unreliable; meaningful catalyst events will emerge only in the final two weeks before settlement. Cross-platform comparison shows prediction markets and traditional weather forecasting services diverge significantly here, with no established sportsbook lines on specific temperature ranges for this date.

Methodology

This page reviews Highest temperature in London on August 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

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

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'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.

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.