Highest temperature in London on June 9?

Platform comparison

Active sub-markets

Market context

On 9 June 2026, the highest temperature recorded at London City Airport will fall into one of several defined ranges. The settlement relies on historical data from Wunderground's archive for that specific station, which sits in East London and typically records slightly warmer readings than central London due to its location and exposure. The 0% crowd probability suggests either extreme confidence in a particular range or minimal trading activity on this particular outcome bucket.

London's June temperatures historically cluster between 18–24°C, with daily highs rarely exceeding 25°C before mid-month. The Met Office's 30-year climate average for early June shows a mean maximum of around 20°C, though outlier days above 28°C occur roughly once per decade. Comparable markets on Kalshi and Betfair have shown tighter liquidity on specific temperature thresholds than on broader ranges, whereas Polymarket's decimal odds format can obscure the true implied probability if traders aren't converting manually. Smarkets' fractional odds display makes probability comparison more transparent across platforms, though KYC requirements vary—Kalshi's US-only access and Betfair's stricter verification contrast with Polymarket's broader international reach, affecting which traders can actually participate.

The UK's weather forecast window extends reliably only 10 days ahead; traders should monitor the Met Office and BBC Weather from late May onwards for any anomalous high-pressure systems or Atlantic weather patterns that might push June 9 into unseasonably warm territory. Atmospheric blocking patterns in early summer can occasionally drive temperatures 5–8°C above the seasonal norm, though such events remain statistically uncommon. Fee structures differ materially: Polymarket charges 2% on both sides, Kalshi takes 0.5%, and Betfair's commission scales with volume, making arbitrage between platforms difficult on low-liquidity weather outcomes.

Methodology

We read Highest temperature in London on June 9? 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

Polymarket settles via UMA Optimistic Oracle on Polygon. A proposer posts the outcome with a bond, the two-hour window runs, then the smart contract pays USDC.

Kalshi settles USD through the CFTC-regulated clearinghouse — the cleanest variant, with heavier KYC. Betfair Exchange settles in account currency (GBP/EUR), net of 2-5% commission. Smarkets follows the same model as Betfair with a lower default 2% commission.

FAQ

Where can I trade this market with the lowest fees?

On Polymarket Alternative, 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.

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.

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 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.