Highest temperature in London on July 20?

Platform comparison

Market context

The market asks for the highest temperature recorded at London City Airport on 20 July 2026, with the crowd currently assigning a 0% probability to the YES outcome for any specific range outside the leading 72–73°F bracket. This implies the consensus firmly expects a mild summer day, ruling out extreme heat events that would push temperatures into the 30°C+ ranges seen in previous record-breaking years.

Historical data for late July in London shows that while heatwaves have occurred, such as the 40.2°C record in 2022, typical highs at City Airport rarely exceed 28°C due to its coastal location and urban cooling effects. The current 0% implied probability for outlier ranges suggests traders view a repeat of such extremes as statistically negligible, favouring the 21–22°C (72–73°F) range as the safe favourite, with little value in betting on underdog scenarios below 18°C unless a sudden cold front develops.

Traders should monitor the Met Office’s five-day forecast and any incoming Atlantic pressure systems, as a shift to southerly winds could elevate temperatures unexpectedly. Recent weather bulletins indicate moderate humidity and falling pressure, which often precede unstable conditions, though no immediate heatwave announcements have been issued [2]. The settlement window closes at 12:00 UTC on 20 July 2026, meaning any late-morning temperature spike would be the sole catalyst for a contrarian play, yet current data offers no support for such a move.

Sources: 1 · 2

Methodology

We track Highest temperature in London on July 20? across the five venues with material prediction-market liquidity. The probability shown is the live Polymarket mid; the comparison rows summarise how each venue treats the underlying contract — fees, KYC thresholds, settlement currency, deposit options. The highlighted row marks the cheapest route into Polymarket's order book.

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

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 Polymarket cost to trade?

Polymarket itself charges 0% — the only cost is the Polygon network fee, typically under $0.01 per transaction. Off-chain venues like Kalshi or Betfair charge 2-7% commission.

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?

On Polymarket directly, no — it's wallet-based. Intermediary brokers like Who Will Win trigger KYC only above $1,500 of lifetime trading volume; under that you trade pseudonymously with a single wallet address.

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.