Highest temperature in London on August 4?

Platform comparison

Market context

London’s outcome depends on the highest reading logged at London City Airport Station before the market’s settlement window closes, so the key question is whether 4 August produces a late-morning or early-afternoon spike rather than the overnight minimum. Seasonal context points to a modest August baseline: London’s average highs are around the low 20s Celsius, while daily forecast products for early August cluster near the low-to-mid 20s, with one source showing about 22°C for 4 August and another implying low- to mid-20s conditions for the first week of the month.[10][11][12]

A 0% “YES” price is hard to reconcile with London’s recent weather pattern, because 2026 has already produced repeated UK heat episodes and London has reached 26.6°C at Kew Gardens during the year, with some reporting calling it the city’s hottest day of 2026 so far.[3][6][9][16] For a settlement based on the day’s maximum, the practical reference is whether London can push materially above typical August norms; in a quiet weather regime, readings in the low 20s are more common than extreme spikes, but a heatwave can lift the range quickly.[7][11][12]

Traders should watch the Met Office and BBC weather updates, any short-notice heat warnings, and the intraday London forecast, because a dry southerly setup can change the maximum by several degrees if cloud cover breaks earlier than expected.[16][18] On the crypto side, this is a USDC-settled on-chain market, so the price mainly reflects probability rather than payout mechanics; BTC and ETH swings matter only indirectly through risk appetite and liquidity conditions, while exchange funding rates or whale flows would be relevant only if the broader market starts repricing weather-event risk alongside crypto beta.

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.

FAQ

What are crypto prediction markets?

Crypto prediction markets are on-chain smart contracts where you buy YES or NO shares on a future crypto event (e.g. "BTC above $100k by year-end"). The market price between 0¢ and 100¢ is the implied probability.

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.

Can I use Bitcoin directly?

No, Polymarket operates exclusively in USDC on Polygon. You can bridge BTC to USDC via an exchange or bridge service and deposit on Polygon — typically 10-30 minutes processing time.

Which crypto markets exist on Polymarket?

Currently active markets include BTC/ETH/SOL price targets, halving dates, ETF approvals, hard-fork outcomes and Layer-2 TVL thresholds. The list updates weekly; biggest volume sits on BTC and ETH price forecasts.

Are crypto prediction markets taxable in the US?

In the US, prediction market gains are typically treated as ordinary income or short-term capital gains depending on holding period. Consult a tax professional for your specific situation — we cannot provide tax advice.