Highest temperature in NYC on July 20?

Platform comparison

Market context

New York City is tracking a record-breaking heatwave for mid-July 2026, with the East Coast simultaneously shattering temperature records that stood for over a century. Historical data from the recent July 4–7 period shows NYC, DC, and Atlantic City breaching long-standing highs, suggesting the 0% implied probability for lower temperatures on July 20 reflects a market anticipating extreme heat rather than a statistical anomaly [2]. On Polymarket, the frontrunner is the 82–83°F range at 100% probability, indicating the crowd expects the LaGuardia Airport Station to record temperatures within this band, whereas traditional books like Kalshi or Betfair would express this as decimal odds of 1.00 rather than a percentage [1].

Traders should monitor the National Weather Service’s extended forecasts and any official heat advisories issued for the tri-state area, as these often precede settlement-confirming temperature spikes. The settlement window closes at 12:00 UTC on 20 July 2026, with Wunderground serving as the definitive resolution source for the LaGuardia station’s daily maximum [1]. Platform divergence is stark here: while Polymarket displays the 100% chance as a clean implied probability, Smarkets and Betfair would require conversion to decimal odds (1.00), and Kalshi’s fee structure and KYC requirements may limit access for users who prefer Polymarket’s lighter verification model. The market’s binary framing against lower ranges ignores the nuance of exact degrees, a limitation some alternative platforms address with finer granularity.

Sources: 1 · 2

Methodology

This page compares Highest temperature in NYC on July 20? specifically across Polymarket, Kalshi, Betfair Exchange and Smarkets. The live probability is the Polymarket mid; the comparison columns summarise each venue's fee structure, KYC, settlement currency and payment rails. Every CTA routes to Polymarket Alternative, 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

What does Polymarket cost vs Kalshi?

Polymarket: 0% fees, only Polygon network costs (~$0.01/trade). Kalshi: up to 7% per trade plus spread. For high-frequency traders, Polymarket is dramatically cheaper.

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.

What about Smarkets as an alternative?

Smarkets is a UK betting exchange with a lower default commission (2%) than Betfair. Liquidity on political markets is below Polymarket, comparable to Kalshi. Geo-blocked in many jurisdictions.

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.