Highest temperature in NYC on July 21?

Platform comparison

Market context

LaGuardia Airport will record a daily high temperature on 21 July 2026, with settlement determined by the maximum reading captured at that station throughout the calendar day. The market bins this outcome into discrete temperature ranges, and the crowd currently assigns zero probability to any single range, suggesting either incomplete market formation or extreme uncertainty about which bracket will validate.

New York City's July climate is well-documented: the National Weather Service records show median highs around 84°F (29°C) for mid-July, with historical extremes reaching into the low 90s Fahrenheit. The 2023 summer saw several days exceed 90°F across the region, whilst the 2021 heatwave pushed readings above 95°F. These precedents establish that outcomes spanning 80–95°F represent the plausible centre of distribution, with tail outcomes (sub-75°F or above 98°F) carrying materially lower frequency. A trader evaluating this market programmatically would anchor on climatological normals and recent seasonal patterns rather than relying on the current flat probability distribution.

Monitoring the National Weather Service forecast cone and Atlantic hurricane tracking becomes material in early July 2026, as tropical systems or upper-level troughs can suppress temperatures significantly. Conversely, high-pressure ridging typically associated with summer anticyclones drives readings toward the upper range. Wunderground's historical archive provides the authoritative settlement source, though traders should verify data availability windows and any station maintenance schedules that might affect readings on the settlement date itself.

Methodology

We track Highest temperature in NYC on July 21? across the five venues with material prediction-market liquidity. The probability shown is the live Polymarket mid; the comparison rows summarise how each venue treats the underlying contract — fees, KYC thresholds, settlement currency, deposit options. The highlighted row marks the cheapest route into Polymarket's order book.

Resolution & payout

Polymarket-based markets settle through the UMA Optimistic Oracle on Polygon. A proposer submits the outcome, a two-hour challenge window opens, and unchallenged proposals finalise the resolution. Payouts settle automatically in USDC the moment the result is final — no bookmaker, no delay.

Kalshi-based markets settle in USD via the CFTC-regulated clearinghouse. Betfair Exchange settles in GBP/EUR net of commission. Manifold is play-money and does not pay out real funds.

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 Polymarket Bot UK. Kalshi charges up to 7% per trade; Betfair Exchange takes 2-5% commission on net winnings.

Is this market available outside the US?

Polymarket itself is geo-blocked in the US/UK/EU. Always check the legal status of prediction markets in your jurisdiction before trading.

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 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 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.