Highest temperature in London on May 20?

Platform comparison

Active sub-markets

Market context

The outcome is determined by the highest temperature logged at London City Airport Station on 20 May, then bucketed into the market’s Celsius range once Wunderground finalises the day’s record. A 0% crowd-implied chance for the YES side suggests the market is already leaning heavily towards a cooler reading, which is consistent with London’s late-May climatology. Historical daily highs in London are often in the mid-teens rather than the high twenties, and even warm spells can be local and brief rather than city-wide.

Comparable late-spring cases show how quickly a single front, cloud bank or sea-breeze shift can cap the day’s maximum below trader expectations. The key reference point is not a seasonal average, but the specific airport station reading, which can differ from central London by a degree or two. For a USDC-settled prediction market, that makes the final Wunderground print the binding event, not broader Met Office headlines or city-average forecasts.

Traders should watch the latest short-range forecast updates, especially any revision to high-pressure cover, wind direction and overnight cloud clearing, because these are the main drivers of the noon-to-afternoon maximum. London City Airport is also sensitive to easterly or onshore flow, which can mute warming even when inland areas rise faster. On the crypto side, BTC and ETH swings matter only indirectly through overall platform risk appetite and liquidity, while on-chain settlement still depends on the market’s final resolution source rather than exchange price action.

Sources: 1 · 2 · 3 · 4 · 5

Methodology

Methodologically this overview focuses on on-chain pricing: Polymarket's live mid comes from the Polygon conditional-token order book and settles automatically in USDC. The other three venues — Kalshi, Betfair, Manifold — are listed with their platform attributes, because they operate off-chain and a 1:1 comparison of contract mechanics isn't possible.

Resolution & payout

Settlement is on-chain via UMA Optimistic Oracle. A proposer posts the outcome with a bond, a two-hour dispute window opens, then the smart contract lifts winning conditional tokens to 1 USDC and sends payments to holders' wallets automatically. No withdrawal fees beyond Polygon gas.

Off-chain venues (Kalshi, Betfair, Smarkets) settle in local fiat through bank-side clearing — faster than SWIFT, slower than on-chain. Manifold pays no real cash.

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.