Highest temperature in London on June 21?

Platform comparison

Active sub-markets

Market context

Polymarket currently prices this London City Airport temperature contract with **29°C** the frontrunner at **32%** and **30°C** close behind at **30%**, so the book is treating a fairly hot late-June outcome as the modal result rather than a tail event.[1] For a trader posting **USDC** on Polygon, the key point is that the contract settles to the highest recorded station temperature for the day, not a forecast peak, and the result will only be fixed once Wunderground has published the following day’s first datapoint for London City Airport.[1][2]

That framing matters because late-June London climate norms sit much lower, with official and climatological baselines around the low 20s Celsius, while current airport observations remain typical of a standard summer day rather than an extreme one.[1][3][4] In practice, a 29°C-or-higher print usually requires a decent warm spell, so the market’s current pricing implies traders are leaning on the possibility of a short-lived heat surge rather than merely average seasonal warmth.[1][4]

For catalysts, the main watchpoint is the day’s intraday temperature path at London City Airport and whether any fresh Met Office or other forecast updates flag a stronger-than-expected afternoon spike, because this market resolves on the *highest* observation, not the daily mean.[6][1] There is no separate corporate or policy dependency here; the decisive inputs are the station’s actual readings and the resolution-source timing, with revisions counted only until the first datapoint for 22 June is published.[2][1]

Sources: 1 · 2 · 3 · 4 · 5

Methodology

This page reviews Highest temperature in London on June 21? across five venues. We show live odds for Polymarket-based markets (sourced from the Polygon order book); for other venues we list platform attributes, since the comparable contracts are not exposed via a public API on every venue. Every CTA points at Polymarket Legit? — the application we operate, where you trade directly against the Polymarket order book at 0% fees.

Resolution & payout

At resolution the UMA oracle takes over: a proposer posts the outcome with a bond, any token holder can dispute within two hours. Without dispute the result is accepted and the smart contract distributes USDC instantly.

On Kalshi (CFTC-regulated) resolution runs through their in-house clearing engine in USD. Betfair Exchange settles after match end in the account's local currency. Manifold pays no cash — only its in-platform "mana" currency.

FAQ

Where can I trade this market with the lowest fees?

On Polymarket Legit?, 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.

Is this market available outside the US?

Polymarket Legit? 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.

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 Polymarket Legit??

Zero. Polymarket Legit? 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, Polymarket Legit? triggers a quick verification flow that finishes in minutes.