Highest temperature in London on June 4?

Platform comparison

Active sub-markets

Market context

On 4 June 2026, London City Airport's weather station will record a daily maximum temperature. The settlement hinges on which range that reading falls into, with resolution sourced from Wunderground's historical data for that specific station and date. The 0% crowd probability suggests traders are either uncertain about the exact range boundaries or treating this as a calibration exercise ahead of the settlement window closing at midday on the day itself.

London's June temperatures historically cluster between 18–24°C, with extremes rare but documented. The Met Office's 30-year averages show mean highs around 21°C for early June, though the city has recorded 28°C+ on occasion during heat waves. Comparable prediction markets on Kalshi and Betfair have shown wider implied probability distributions for UK temperature ranges, partly because those platforms' decimal-odds displays and fee structures (Kalshi's 2% settlement fee versus Betfair's commission model) create different breakeven thresholds for traders pricing tail-risk scenarios. Polymarket's percentage-based interface may obscure whether the 0% reflects genuine conviction or merely sparse liquidity in a niche weather contract.

Traders should monitor the UK Met Office's long-range forecast updates through May 2026, particularly any signals of anomalous warmth or cool patterns. Atmospheric blocking patterns and jet-stream positioning in late spring will determine whether June 4 falls within seasonal norms or deviates significantly. The settlement window's tight closure—midday on the event date itself—leaves no room for post-event price discovery, making pre-event positioning critical and distinguishing this market's risk profile from longer-window alternatives on competing platforms.

Methodology

We read Highest temperature in London on June 4? from four platform perspectives: Polymarket (on-chain CLOB), Kalshi (CFTC-regulated exchange), Betfair Exchange (sports book exchange), Smarkets (peer-to-peer betting exchange). Polymarket's live quote comes directly from the Polygon order book; the other three are listed with their platform attributes — fees, KYC, settlement currency, payment options — because a 1:1 contract comparison without API access would be guesswork.

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 Polymarket 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 does it cost to trade on Polymarket Alternative UK?

Zero. Polymarket Alternative UK routes every order to the live Polymarket order book; the only cost is the Polygon network fee, typically under $0.01 per transaction.

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, Polymarket Alternative UK triggers a quick verification flow that finishes in minutes.