Highest temperature in London on May 31?

Platform comparison

Active sub-markets

Market context

On 31 May 2026, the highest temperature recorded at London City Airport will fall into one of several defined ranges. The market settles on data from Weather Underground's historical records for that specific station, which sits in East London and typically captures urban heat-island effects that can elevate readings relative to surrounding areas. The 0% crowd probability suggests traders are either absent from this particular contract or treating it as a placeholder ahead of seasonal forecasting becoming actionable.

London's May temperatures have historically peaked between 24–28°C in recent decades, with occasional excursions into the low 30s during heat waves. The May 2022 heat event saw temperatures reach 28°C in parts of London, whilst May 2020 delivered a 29°C maximum. City Airport, positioned near the Thames and surrounded by built environment, tends to register slightly higher maxima than central London parks. Traders comparing Polymarket's decimal-odds interface against Kalshi's implied-probability format will find the latter's clearer percentage display useful for seasonal weather markets where base rates matter; Betfair and Smarkets offer tighter liquidity on UK-specific weather but charge commission structures that erode edge on low-probability outcomes.

The Met Office's seasonal outlook and any late-May Atlantic blocking patterns will shape trader positioning in the final weeks before settlement. High-pressure systems anchored over the UK in late spring typically drive the warmest May days; conversely, Atlantic troughs can suppress maxima into the low 20s. Real-time forecast consensus from mid-May onwards will likely trigger rebalancing across all platforms, though Polymarket's lower KYC friction may attract late-entry speculators unfamiliar with UK meteorology.

Methodology

We read Highest temperature in London on May 31? 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

Settlement is the biggest difference between the four platforms: Polymarket on-chain in USDC (instant), Kalshi USD via CFTC (T+1), Betfair and Smarkets in local currency via bank withdrawal (T+1 to T+3). Polymarket Alternative routes every trade directly into Polymarket's on-chain settlement, which is why payouts land fastest.

FAQ

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 it cost to trade on Polymarket Alternative?

Zero. Polymarket Alternative 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 triggers a quick verification flow that finishes in 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.