Highest temperature in NYC on July 21?

Platform comparison

Market context

New York City's highest temperature on 21 July 2026 will be recorded at LaGuardia Airport and settled against historical weather data from Wunderground. The settlement window closes at midday UTC, meaning traders must account for the full calendar day's temperature range before the market locks. This particular date falls in the peak of summer, when New York typically experiences sustained heat and humidity; July averages daily highs near 27–29°C (80–84°F), though heat waves can push readings significantly higher.

Historical precedent matters here. New York's all-time July record stands at 40°C (104°F), set in 1966, whilst more recent heat events—including the July 2019 spike to 34°C (93°F) and the summer 2022 heat dome—show that extreme outliers remain plausible but rare. The 0% crowd probability currently implied across prediction platforms suggests either extreme scepticism about a record-breaking event or minimal trading volume on this specific date range. Kalshi and Betfair typically offer tighter decimal odds on weather markets than Polymarket's AMM-style pricing, which can create arbitrage opportunities when liquidity fragments across venues.

Traders should monitor the National Weather Service's extended forecast for late July 2026 and track any Atlantic hurricane activity or upper-level atmospheric patterns that could suppress temperatures. Unlike political or sports markets, weather prediction markets reward those who integrate meteorological models rather than sentiment alone. The Wunderground data source is publicly accessible and non-discretionary, eliminating settlement disputes common to other event categories.

Methodology

We read Highest temperature in NYC on July 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 mid is the canonical probability; the side-by-side columns benchmark fees, KYC, settlement currency and deposit rails so you can choose the venue that fits your jurisdiction and trade size.

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

Polymarket vs Kalshi — which is better?

Depends on your location. Kalshi is CFTC-regulated, US-only with full KYC. Polymarket is global, on-chain, no KYC up to $1,500. Polymarket has ~10x higher liquidity but higher regulatory risk.

Which platform has the deepest liquidity?

Polymarket — by a wide margin. Top markets reach $50-500M volume, Kalshi ~$200M cumulative, Betfair similar. Deeper liquidity means your trade moves the quote less.

Is Betfair a Polymarket alternative?

Only partially. Betfair Exchange is UK-focused with a sports-betting emphasis; they have politics markets but with thinner liquidity than Polymarket. Settlement in GBP/EUR, 2-5% commission on winnings.

Which platform is accessible globally?

Polymarket is geo-blocked in the US/UK/EU. Kalshi is US-only. Betfair and Smarkets are UK-restricted. Polymarket Alternative has a different geo footprint and routes to Polymarket's order book at 0% fees.

Are all these platforms regulated?

No. Kalshi is CFTC-regulated (US). Betfair and Smarkets are UK Gambling Commission licensed. Polymarket operates without explicit regulation — a different risk profile than a regulated sportsbook.