Highest temperature in London on May 23?

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Market context

The settlement hinges on the single highest temperature recorded at London City Airport on 23 May 2026, measured in Celsius and resolved via Wunderground historical data. The 0% crowd probability suggests traders are either uncertain about range placement or waiting for seasonal context to crystallise before committing capital.

Late May in London typically sees daytime highs between 18–22°C, though the airport station—positioned near the Thames estuary—experiences maritime moderation that can suppress peaks compared to inland readings. Historical May 23rd data from the Met Office shows London has recorded highs ranging from 15°C in cooler years to 26°C during warm spells, with the long-term average sitting around 20°C. The absence of trading activity at 0% suggests the market may lack sufficient granularity in its temperature bands to attract early positioning, or traders are deferring until spring 2026 forecasting models become more reliable.

Catalysts for movement centre on the Atlantic weather pattern and high-pressure systems tracking into northern Europe during late May. The UK's seasonal transition into early summer typically brings variable conditions—warm southerly airflows can push temperatures sharply upward, whilst Atlantic lows can suppress them. Traders should monitor the Met Office's monthly outlook for May 2026 once issued in April, and track any anomalies in sea-surface temperatures in the North Atlantic that might signal sustained warmth. The settlement window closes at midday on 23 May, meaning the market resolves based on morning and early-afternoon temperatures only, favouring scenarios where high pressure dominates rather than afternoon thunderstorms that could cap peaks.

Methodology

We track Highest temperature in London on May 23? on the five venues with material liquidity for prediction markets. Live odds come from the Polymarket Polygon order book — the only source that ships real-time data under an open licence. For Kalshi, Betfair and Manifold we list platform attributes (fee, KYC, settlement, payment) instead of fabricated odds, because their APIs use non-comparable contract definitions.

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?

PolyGram is available in most jurisdictions where Polymarket isn't directly accessible. Polymarket itself is geo-blocked in the US/UK/EU. Always check local regulations.

What does it cost to trade on PolyGram?

Zero. PolyGram 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, PolyGram 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.