Highest temperature in London on August 6?

Platform comparison

Market context

London’s hottest reading at the airport station is what settles this market, and the contract is effectively a bet on whether Heathrow-style summer warmth shows up at London City Airport before the midday cut-off in Wunderground’s daily history page. With the current crowd-implied price at 0% YES, the market is signalling that traders see the required top-end temperature band as unlikely, not impossible, and the path to settlement depends on a single station’s recorded maximum rather than a citywide average.

The historical frame is mixed: London’s August climate norm is milder than the very hot spells that have occasionally hit southern England, with typical daily highs around the high teens Celsius, but the UK has also seen repeated heat episodes in 2026, including days above 32°C and a reported 26.6°C at Kew Gardens that was the hottest day of the year so far at that point.[13][14][15][16] That matters because airport stations can run warmer than central London in clear, dry conditions, yet they still need the right combination of sunshine, low cloud and light wind to push into the upper ranges that would move this contract out of the lowest buckets.

For traders, the key catalysts are the day’s local forecast updates, any shift in cloud cover or wind, and whether the wider UK pattern remains hot enough to drag London into the low-30s Celsius band.[1][4][16] In crypto terms, there is no obvious BTC or ETH linkage beyond general risk appetite: the real driver is the weather print itself, which will settle in USDC on-chain once the oracle or market rules map the London City Airport observation to the stated range.

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 — sit alongside as off-chain reference points so you can see how the contract translates across regulatory and settlement regimes.

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.

UK Frequently Asked Questions

Why USDC and not ETH or USDT?

USDC is the Polygon standard — audited reserves (Circle, monthly attestation), deepest order book, low gas costs. ETH volatility would distort probability quotes; USDT has thinner Polygon liquidity than USDC.

What does a transaction cost on Polygon?

Polygon gas is typically under $0.01 per transaction. A full trade cycle (Approve + Order + Fill) totals around $0.03 — compared to $5-50 on Ethereum mainnet.

Is Polymarket legal in the UK?

Polymarket is accessible to UK traders but is not UKGC-licensed. It operates under US CFTC jurisdiction. UK residents face no domestic legal prohibition on using it, but UKGC consumer protections do not apply. For UKGC-regulated alternatives, Betfair Exchange and Smarkets offer similar prediction-style markets.

Do I pay tax on prediction market profits in the UK?

UKGC-licensed platform profits (Betfair, Smarkets) are typically tax-free gambling winnings for UK individuals. Polymarket profits involve USDC crypto transactions, which HMRC treats as Capital Gains Tax events. Keep full transaction records and report via Self Assessment if gains exceed £3,000 per tax year.

How do I deposit on Polymarket from the UK?

UK traders typically fund Polymarket via Coinbase UK, Kraken or Revolut — buying USDC with GBP and transferring to a Polygon-compatible wallet (MetaMask, Coinbase Wallet). Polymarket's onboarding walks you through the bridging process. Typical GBP-to-USDC conversion costs 0.5–1%.