Highest temperature in London on June 21?

Platform comparison

Active sub-markets

Market context

The relevant event is the **highest observed temperature at London City Airport Station on 21 June**, settled against Wunderground’s daily history page for the station. Late-June London typically sits around the low 20s Celsius, so outcomes in the upper 20s are materially above the seasonal norm rather than extreme outliers.[1][4][5]

A 0% crowd-implied probability is only a snapshot of current sentiment, not a statement about final weather. Comparable London summer temperature markets tend to cluster around the forecast-driven band rather than the climatological average: for example, recent Polymarket temperature contracts for London have been priced tightly around a single daytime maximum when short-range forecasts were clearer, showing how quickly these markets can reprice as model consensus changes.[2][1] The presence of nearby bands such as **29°C** and **30°C** in the current market structure indicates that traders are already focusing on a hot-tail outcome rather than a middling June reading.[1]

From a market-access and compliance angle, this kind of weather contract sits at the intersection of local gambling rules and broader derivatives oversight. In Germany, the GlüStV can matter because prediction markets may be treated as gambling-like products depending on structure and availability, which can affect access and promotion. In the US, the CFTC’s reach is relevant because event contracts can raise federal commodities-law questions if offered to US persons. “No-KYC up to $1,500” means a user can typically participate without identity verification until cumulative activity reaches that threshold, which can make the market easier to access for small positions but does not remove jurisdictional restrictions or platform-level compliance checks.[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 Legal UK — 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 Legal UK, 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.

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 does it cost to trade on Polymarket Legal UK?

Zero. Polymarket Legal UK routes every order to the live Polymarket order book; the only cost is the Polygon network fee, typically under $0.01 per transaction.

How fast are USDC deposits?

Polygon credits deposits after 12 confirmations — usually under 30 seconds. Withdrawals follow the same path and land back in your wallet within minutes.

Do I need to KYC for this market?

Not under $1,500 of lifetime trading volume. Above that threshold, Polymarket Legal UK triggers a quick verification flow that finishes in minutes.