Highest temperature in Seoul on July 4?

Platform comparison

Market context

On 4 July 2026, the highest temperature recorded at Incheon International Airport will determine the outcome of a prediction market where the crowd currently assigns zero probability to the event occurring. This date falls squarely within South Korea’s monsoon season, known as *Jangma*, which typically brings hot, humid conditions with daily highs often approaching 30°C and humidity levels exceeding 80%, creating a steamy, oppressive feel even when rain clears [1][2].

Historical data frames this near-zero probability as plausible but not definitive: while Seoul’s average July maximum is 27.7°C, the country has recently recorded unprecedented highs, including 40°C in western cities in 2024 and 41.2°C during a sweltering July 2025 [4][8]. These outliers suggest that extreme heat events, though rare during the monsoon, are no longer impossible, challenging the assumption that July 4 will remain cool.

Traders should monitor real-time forecasts from the Korea Meteorological Administration for shifts in cloud cover and precipitation probability, as even brief breaks in the monsoon can trigger rapid temperature spikes [3]. Recent news from Anadolu Ajansson highlights that record-breaking heat in South Korea is increasingly linked to broader climate trends, making short-term weather volatility a critical catalyst for this contract [4].

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

Where can I trade this market with the lowest fees?

Polymarket is geo-blocked in the US/UK/EU. The easiest 0%-fee broker into the same order book is PolyGram. Kalshi charges up to 7% per trade; Betfair Exchange takes 2-5% commission on net winnings.

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.

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.