Highest temperature in Seoul on June 21?

Platform comparison

Active sub-markets

Market context

The relevant event is the day’s peak temperature at Incheon International Airport Station, which is the settlement source rather than a citywide Seoul reading. On the current Polymarket board, the market is clustered around the **26–28°C** band, with **27°C** shown as the frontrunner and **26°C** the next closest outcome, which is consistent with a late-June climate in Seoul that typically produces average highs near **26°C** and can occasionally push into the upper 20s.[1][2][3]

That framing matters when comparing venues. Polymarket displays outcome-by-outcome **implied probabilities** directly, while Kalshi and many sportsbook-style books such as Betfair and Smarkets often present **decimal odds** first, so the same temperature band can look less or more aggressive depending on the format and the fee line. For a market currently priced at **0% YES** on one platform, the key question is not whether 30°C is impossible, but whether the listed temperature buckets on the venue align with the settlement source’s observed high and any rounding rules; that is where cross-book quoting can diverge, especially if one exchange has thinner liquidity or uses a different fee model.

The main catalysts are weather-model updates, synoptic changes over the Korean Peninsula, and any shift in humidity, cloud cover, or rainfall timing that could cap the afternoon high. June heat in South Korea has been strong enough to produce record-breaking conditions in recent years, including a widely reported surge in summer heat and record June temperatures, so traders will be watching whether the day trends towards a dry, sunny outcome or a more muted high under cloud and showers.[7][9] KYC access also differs by platform: Polymarket and its competitors do not offer identical geographic reach, and that affects who can participate as the settlement clock runs down.

Sources: 1 · 2 · 3 · 4 · 5

Methodology

We read Highest temperature in Seoul on June 21? from four platform perspectives: Polymarket (on-chain CLOB), Kalshi (CFTC-regulated exchange), Betfair Exchange (sports book exchange), Smarkets (peer-to-peer betting exchange). Polymarket's live quote comes directly from the Polygon order book; the other three are listed with their platform attributes — fees, KYC, settlement currency, payment options — because a 1:1 contract comparison without API access would be guesswork.

Resolution & payout

Settlement is the biggest difference between the four platforms: Polymarket on-chain in USDC (instant), Kalshi USD via CFTC (T+1), Betfair and Smarkets in local currency via bank withdrawal (T+1 to T+3). Kalshi Alternative UK routes every trade directly into Polymarket's on-chain settlement, which is why payouts land fastest.

FAQ

Where can I trade this market with the lowest fees?

On Kalshi Alternative UK, which mirrors the Polymarket order book at 0% fees. 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 it cost to trade on Kalshi Alternative UK?

Zero. Kalshi Alternative UK routes every order to the live Polymarket order book; the only cost is the Polygon network fee, typically under $0.01 per transaction.

Do I need to KYC for this market?

Not under $1,500 of lifetime trading volume. Above that threshold, Kalshi Alternative UK triggers a quick verification flow that finishes in 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.