Highest temperature in London on August 11?

Platform comparison

Market context

On 11 August 2026, the highest temperature recorded at London City Airport will determine this market's resolution, with the figure drawn from Weather Underground's Daily Observations table rather than their summary high-low display. The distinction matters: intraday observation logs sometimes diverge from headline figures, and the platform has specified the granular data source to avoid ambiguity. Current crowd pricing shows 0% implied probability, suggesting traders expect temperatures to fall outside whatever range bracket this market offers—a signal worth interrogating against historical August patterns for the capital.

London's August temperatures typically peak between 20–24°C, with extremes rare but documented. The 2022 heatwave saw readings exceed 40°C across parts of the UK, though City Airport itself recorded lower maxima due to its riverside location and urban heat-sink effects. August 2003 reached 38.1°C in London; more recently, August 2023 peaked around 19°C. The 0% crowd reading suggests either the market's temperature brackets are pitched conservatively high, or traders are anchoring to cooler recent Augusts rather than tail-risk scenarios. Comparing across platforms: Kalshi typically offers tighter decimal-odds precision than Betfair's fractional format, whilst Smarkets' fee structure (around 2% commission) differs from Polymarket's variable taker fees. KYC requirements vary—Kalshi enforces stricter US-focused verification than some offshore alternatives.

Traders should monitor the UK Met Office's long-range forecast issued in late July 2026, which will clarify whether high-pressure systems or Atlantic weather systems dominate that week. Seasonal patterns favour cooler conditions in early August relative to late July, though climate trends have shifted baseline expectations upward over the past decade.

Methodology

This page compares Highest temperature in London on August 11? specifically across Polymarket, Kalshi, Betfair Exchange and Smarkets. The live probability is the Polymarket mid; the comparison columns summarise each venue's fee structure, KYC, settlement currency and payment rails. Every CTA routes to Kalshi Alternative UK, which mirrors the Polymarket order book at 0% fees.

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.

UK Frequently Asked Questions

Polymarket vs Kalshi — which is better?

Depends on your location. Kalshi is CFTC-regulated, US-only with full KYC. Polymarket is global, on-chain, no KYC up to $1,500. Polymarket has ~10x higher liquidity but higher regulatory risk.

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.

Polymarket vs Betfair Exchange: which is better for UK prediction trading?

Betfair Exchange offers UKGC regulation, GBP settlement, and potentially tax-free winnings — but focuses on sports and politics only. Polymarket has deeper liquidity, 0% platform fee, global event coverage, and crypto/geopolitical markets Betfair doesn't offer. For UK traders: Betfair for regulated GBP sports markets; Polymarket for broader, global prediction events.

Is Kalshi available in the UK?

Kalshi is a US CFTC-regulated prediction exchange. UK residents can create accounts but must use USD and US payment methods. Kalshi's product range overlaps with Polymarket but with lower liquidity on most contracts. For UK traders, Polymarket typically offers better prices due to higher global volume.