Highest temperature in London on June 28?

Platform comparison

Market context

The real-world event centres on the highest temperature recorded at London City Airport on 28 June 2026, with the market currently implying a 0% chance of the “YES” outcome. Historical data shows that late June in London typically sees highs around 24–26°C, though recent anomalies have pushed temperatures significantly higher. For instance, on 24 June 2026, the UK recorded its hottest June day ever at 34.8°C, and London hit 36.4°C just days prior, with Heathrow reaching 40.2°C [6][8]. Even on 27 June 2026, London City Airport recorded a maximum of 31.1°C, well above the seasonal average [9]. These precedents suggest that while extreme heat is possible, the current 0% probability may reflect a conservative model or a specific threshold that is unlikely to be breached.

Traders should monitor the Met Office’s daily forecasts and any heatwave advisories issued for Greater London, as these directly influence temperature outcomes [5]. The National Weather Service and BBC Weather both report current conditions at London City Airport, including southerly winds and falling pressure, which can signal incoming warm air [2][3]. Additionally, Wunderground’s historical data will be the official resolution source, so traders must ensure they interpret Celsius readings correctly via the platform’s gear icon. Platforms like Polymarket, Kalshi, Betfair, and Smarkets diverge notably here: Polymarket and Kalshi use implied probabilities, while Betfair and Smarkets rely on decimal odds; fee structures and KYC requirements also vary, affecting liquidity and accessibility for this specific weather event [1].

Sources: 1 · 2 · 3 · 4 · 5

Methodology

We read Highest temperature in London on June 28? 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

Settlement is the biggest difference between the four platforms: Polymarket on-chain in USDC (instant), Kalshi USD via CFTC (T+1), Betfair and Smarkets in local currency via bank withdrawal (T+1 to T+3). On-chain settlement clears in minutes — the fastest payout path of the four.

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.

Which platform is accessible globally?

Polymarket is geo-blocked in the US/UK/EU. Kalshi is US-only. Betfair and Smarkets are UK-restricted. Robinhood Prediction Markets 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.

Which platform supports Klarna/SOFORT?

Directly: none. Polymarket accepts only USDC on Polygon. Robinhood Prediction Markets offers a fiat on-ramp via Klarna or SOFORT (DE/AT/CH) and converts internally to USDC for the Polymarket order book. T+1 processing.