Highest temperature in NYC on June 21?

Platform comparison

Active sub-markets

Market context

The key real-world event is the highest reading at LaGuardia Airport on 21 June, and the market is really asking whether the day tops out in a normal summer band or breaks into an unusually hot one. Polymarket’s current crowd view at 0% YES is a probability format, while Betfair and Smarkets would usually show the same view through decimal prices and a spread, so the headline number is not directly comparable unless you convert for fees and margin. On Kalshi, the contract settlement depends on the exact Wunderground LaGuardia daily high, which makes airport observations more relevant than broader NYC averages.

Historical context points to a fairly wide June 21 ceiling: the date record in New York City history is 97°F, while Kennedy’s climate normal for the day is 79°F with a 98°F record, showing that very hot outcomes are possible but uncommon.[6][7] Recent June temperature markets on prediction platforms have often clustered around ordinary-to-warm ranges rather than extremes, with one Polymarket NYC daily-high market for 19 June trading entirely in an 82–83°F bucket.[2] For a comparison-minded trader, Kalshi and Polymarket in the US are generally gated by KYC and jurisdiction, whereas Betfair and Smarkets can offer broader UK-facing access but with different market structure and commission models.

The main catalysts are the weather forecast updates and any heat advisories, because small changes in cloud cover, humidity, and wind can move a single-day airport high by several degrees. AccuWeather’s June outlook for New York shows daily highs mostly in the 73–88°F range, which would leave the market vulnerable to upside if a heat plume strengthens, but still far from the historical June extremes.[3] A recent heatwave report for New York described intense sunshine, high humidity, and dangerous heat across the region, with thermometers reaching 102°F in the wider area, which is the kind of setup that can rapidly reprice daily high-temperature contracts.[1]

Sources: 1 · 2 · 3 · 4 · 5

Methodology

This page compares Highest temperature in NYC on June 21? specifically across Polymarket, Kalshi, Betfair Exchange and Smarkets. Live odds come from the Polymarket order book; the other venues' contract details are maintained manually because their APIs aren't directly comparable. Every CTA routes to Kalshi Alternative UK, which mirrors the Polymarket order book at 0% fees.

Resolution & payout

Polymarket settles via UMA Optimistic Oracle on Polygon. A proposer posts the outcome with a bond, the two-hour window runs, then the smart contract pays USDC.

Kalshi settles USD through the CFTC-regulated clearinghouse — the cleanest variant, with heavier KYC. Betfair Exchange settles in account currency (GBP/EUR), net of 2-5% commission. Smarkets follows the same model as Betfair with a lower default 2% commission.

FAQ

Is this market available outside the US?

Kalshi Alternative UK is available in most jurisdictions where Polymarket isn't directly accessible. Polymarket itself is geo-blocked in the US/UK/EU. Always check local regulations.

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's the difference between YES and NO shares?

A YES share pays $1.00 if the event happens, $0 otherwise. A NO share pays $1.00 if the event doesn't happen. The market price between 0¢ and 100¢ is the implied probability.

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.