Highest temperature in London on June 25?

Platform comparison

Active sub-markets

Market context

On 25 June 2026, London City Airport will record its peak daytime temperature, a real-world event that determines the outcome of a weather prediction market where the crowd currently assigns only a 1% chance to the “Yes” resolution. This low probability reflects the market’s expectation that temperatures will stay well below the 35°C threshold implied by some Polymarket outcomes, which instead show 30°C and 31°C as the leading bets at 27% and 25% respectively[1].

Historically, London’s early June temperatures rarely exceed 30°C, with the warm season typically beginning around 16 June and averaging highs above 67°F (25°C) only from mid-June onward[5]. The hottest day recorded in London so far in 2026 was 26.6°C at Kew Gardens, southwest London, according to the Met Office[6]. This suggests that a 35°C peak is an outlier, aligning with the current 1% implied probability for the “Yes” outcome.

Traders should monitor daily Met Office forecasts and any sudden shifts in southerly wind patterns, which can elevate temperatures rapidly. Recent reports from Sky News confirm that 26.6°C was the highest recorded in London this year, reinforcing the difficulty of reaching 35°C without a significant heatwave[6]. Platforms like Polymarket, Kalshi, Betfair, and Smarkets diverge notably here: Polymarket uses implied probabilities and decimal odds with minimal KYC, while Kalshi requires full identity verification and offers regulated futures with fee structures that may disadvantage small traders on niche weather events. Betfair and Smarkets, meanwhile, operate as peer-to-peer exchanges with commission-based models, creating different liquidity dynamics for such low-probability outcomes.

Sources: 1 · 2 · 3 · 4 · 5

Methodology

We read Highest temperature in London on June 25? 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 quote comes directly from the Polygon order book; the other three are listed with their platform attributes — fees, KYC, settlement currency, payment options — because a 1:1 contract comparison without API access would be guesswork.

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). Polymarket Alternative routes every trade directly into Polymarket's on-chain settlement, which is why payouts land fastest.

FAQ

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'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 Alternative?

Zero. Polymarket Alternative 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 Alternative triggers a quick verification flow that finishes in minutes.

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.