Highest temperature in London on May 22?

Platform comparison

Active sub-markets

Market context

London’s afternoon warmth has already been set, and the remaining question is whether the highest reading at London City Airport can still be pushed into the upper twenties before the day closes. With settlement tied to the day’s maximum at the airport station, the market has effectively been left to price whether late sunshine and any further advection can add another degree or two. The crowd is currently assigning 0% to the specific YES outcome being referenced, which points to a view that the forecast peak is already in hand.

For late May, London can produce sharp one-day spikes, but the climatological base rate still sits well below today’s extreme. WeatherSpark shows average highs in London rising from about 16°C at the start of May to around 19°C by month-end, with 27°C a marked outlier rather than a typical late-spring finish. London’s record May maximum is 32.8°C, set in 1922, so the event is not meteorologically impossible, only uncommon enough that markets usually demand a very specific hot setup to pay it.

Traders should watch the final Met Office and local forecast updates, plus any last-mile changes in cloud cover, sea-breeze influence, or wind direction around the Thames corridor, since those can be decisive for an airport station reading. The relevant Wunderground history page for London City Airport will be the settlement source once the day finalises, so any late data adjustments or station quirks matter more than broader London averages. The key dependency is whether conditions stay clear enough for the station to register a fresh peak after midday, or whether the maximum has already occurred.

Sources: 1 · 2 · 3 · 4 · 5

Methodology

We track Highest temperature in London on May 22? 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

At resolution the UMA oracle takes over: a proposer posts the outcome with a bond, any token holder can dispute within two hours. Without dispute the result is accepted and the smart contract distributes USDC instantly.

On Kalshi (CFTC-regulated) resolution runs through their in-house clearing engine in USD. Betfair Exchange settles after match end in the account's local currency. Manifold pays no cash — only its in-platform "mana" currency.

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.

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 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.

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.