Highest temperature in London on May 27?

Platform comparison

Active sub-markets

Market context

On 27 May 2026, the highest temperature recorded at London City Airport will settle into one of several defined ranges. The settlement source is Wunderground's historical weather data for that specific station, measured in Celsius. The 0% crowd probability suggests traders are either absent from this market or systematically underweighting certain temperature bands—a common pattern in niche weather markets where liquidity clusters around round numbers or extreme outcomes.

London's May temperatures typically range between 15°C and 22°C, with historical highs occasionally reaching 25–27°C during warm spells. The Met Office's 30-year average for late May sits around 19°C, though the 2022 heatwave saw readings exceed 28°C in parts of the South East. City Airport, located on the Thames estuary, tends to record slightly cooler maxima than central London due to water proximity. Comparing across platforms: Kalshi's binary structure would force a single threshold choice, whilst Betfair and Smarkets offer range-based markets with decimal odds that better reflect granular probability shifts. Polymarket's fee structure (2% maker, 2% taker) differs materially from Kalshi's flat commission, affecting edge calculations on low-probability tail outcomes.

Traders should monitor the UK long-range forecast issued by the Met Office in early May, which typically refines seasonal patterns into actionable weekly guidance. Bank holiday weekend weather (25–26 May) often influences public discussion and media coverage, potentially shifting sentiment on the 27th. Atmospheric pressure systems tracking across the Atlantic in late April will determine whether high-pressure systems establish over the UK, a key catalyst for above-average May temperatures.

Methodology

This page compares Highest temperature in London on May 27? specifically across Polymarket, Kalshi, Betfair Exchange and Smarkets. Live odds come from the Polymarket order book; the other venues' contract details are maintained manually because their APIs aren't directly comparable. Every CTA routes to Kalshi Alternative UK, which mirrors the Polymarket order book at 0% fees.

Resolution & payout

Polymarket settles via UMA Optimistic Oracle on Polygon. A proposer posts the outcome with a bond, the two-hour window runs, then the smart contract pays USDC.

Kalshi settles USD through the CFTC-regulated clearinghouse — the cleanest variant, with heavier KYC. Betfair Exchange settles in account currency (GBP/EUR), net of 2-5% commission. Smarkets follows the same model as Betfair with a lower default 2% commission.

FAQ

Where can I trade this market with the lowest fees?

On Kalshi Alternative UK, which mirrors the Polymarket order book at 0% fees. Kalshi charges up to 7% per trade; Betfair Exchange takes 2-5% commission on net winnings.

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 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?

Not under $1,500 of lifetime trading volume. Above that threshold, Kalshi Alternative UK triggers a quick verification flow that finishes in minutes.