Highest temperature in Seoul on July 4?

Platform comparison

Market context

Seoul’s July 4 high temperature hinges on whether the day reaches exactly 29°C, a specific bracket within a historically wide early-July range. The Korea Meteorological Administration records show early July highs typically cluster between 27°C and 31°C, with 29°C sitting at the centre of this band. Historical data from 1973 confirms July 2025 was South Korea’s second-hottest July, averaging 27.1°C, while 2023 saw Seoul hit 37.7°C—the highest early July temperature in 117 years. Despite this volatility, the current prediction market implies a 0% probability for the 29°C YES outcome, whereas another platform lists NO at 66% implied probability, reflecting a fragmented field where no single bracket commands majority support.

Traders should monitor the Korea Meteorological Administration’s forecast updates before the noon KST resolution window, as thin volume below $1M means prices can shift sharply on new data. Recent reports highlight a streak of super-hot tropical nights in Seoul, with overnight temperatures exceeding 25°C for 22 consecutive days, breaking a century-old record and suggesting sustained heat pressure. This pattern, combined with the North Pacific high-pressure system’s influence, often drives daytime highs toward 35°C. Analysts note that while 29°C is the single most likely outcome by market consensus, it remains a minority call, with six other temperature brackets sharing the remaining probability. The divergence between sportsbook lines and prediction-market implied probability underscores the uncertainty inherent in forecasting a single day’s peak temperature within such a volatile seasonal window.

Sources: 1 · 2 · 3 · 4 · 5

Methodology

Methodologically we separate two layers: the live probability (Polymarket mid-price) and the platform attributes (fee, KYC, settlement currency, payment rails). That keeps the comparison honest — a single canonical probability across the row, with the venue-by-venue trade-offs spelt out in the columns next to it.

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 Best Prediction Markets UK 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.