Platform comparison
| Platform | YES odds | NO odds | Fee | KYC | Settlement | |
|---|---|---|---|---|---|---|
Polymarket (via BTC Prediction) Pick polygram.ink (preferred broker) |
51% | 49% | 0% (USDC on-chain) | No-KYC up to $1,500 | USDC, auto via UMA oracle | Open live market → |
Polymarket (direct) polymarket.com |
51% | 49% | 0% | Geo-blocked in US/UK/EU | USDC, on-chain | Open live market → |
Kalshi kalshi.com |
— | — | Up to 7% per trade | US-only, KYC required | USD | Open live market → |
Betfair Exchange betfair.com |
— | — | 2-5% commission | Full KYC from first trade | GBP / EUR | Open live market → |
Manifold Markets manifold.markets |
— | — | Play-money (mana) | None — play-money | Mana (no cash-out) | Open live market → |
Outcome probabilities
Current market-implied probability for each outcome, from the live order book.
| Outcome | Probability |
|---|---|
| 26°C | 51% |
| 27°C | 33% |
| 28°C | 6% |
| 29°C | 1% |
| 30°C | 1% |
| 22°C or below | 0% |
| 23°C | 0% |
| 24°C | 0% |
| 25°C | 0% |
| 31°C | 0% |
| 32°C or higher | 0% |
Market context
Seoul's summer temperatures in mid-August typically peak between 28°C and 32°C, though heat waves can push readings above 33°C. The settlement mechanism relies on Weather Underground's Daily Observations table from Incheon International Airport Station, which records sub-hourly readings and differs from the simplified Day High & Low summary. This distinction matters: the Daily Observations capture transient spikes that may not appear in rounded daily summaries, making resolution sensitive to measurement granularity and timing.
Historical August 16 data at Incheon shows considerable variance. In 2023, the high reached 31.2°C; in 2022, 30.1°C; in 2021, 32.8°C. The 0% crowd probability suggests traders are pricing in either extreme confidence in a sub-28°C outcome or liquidity constraints limiting participation. South Korea's meteorological agency forecasts are typically published 10–14 days ahead, with updates every 6 hours. Watch for tropical cyclone activity in the Western Pacific during early-to-mid August 2026, which could suppress temperatures or trigger sudden spikes depending on system trajectory and timing relative to the settlement window (ending 12:00 UTC on August 16).
The USDC settlement structure ties resolution to a single, verifiable data point with no discretion, reducing counterparty risk. Traders should monitor Korea Meteorological Administration advisories and Incheon airport weather station maintenance schedules, as sensor downtime or recalibration could affect Daily Observations availability. Funding rates on weather derivative proxies remain thin, so entry and exit liquidity may constrain position sizing.
Methodology
This page reads Highest temperature in Seoul (Incheon) on August 16? on-chain. Polymarket's quote comes directly from the Polygon order book — the only comparable venue with on-chain settlement. Kalshi (USD, off-chain), Betfair (GBP/EUR, off-chain) and Manifold (play-money) are listed alongside for venue context. Every CTA routes to BTC Prediction, which mirrors the Polymarket order book directly.
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%.
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