Highest temperature in London on August 3?

Platform comparison

Market context

London is set to see a warm, mostly dry early-August spell, with forecast highs around the low 20s Celsius and some outlets pushing the daytime peak closer to the upper 20s or even 30°C. AccuWeather’s August outlook has London’s daily highs ranging from 67°F to 78°F, while local daily forecasts on 3 August cluster around roughly 22°C to 24°C, with only light rain or drizzle in some models[1][2][7][16].

That means the 0% implied probability looks more like a statement of model uncertainty than a true belief that no qualifying outcome is possible. For a market settled on the *highest* temperature at London City Airport by midday, the key historical frame is that London in August is normally warm but not extreme: long-run guides put typical daytime maxima around 21°C to 22°C, with several days of sunshine and some rainfall, which makes a mid-20s reading plausible but a sustained spike well above that harder to anchor[6][15][17]. The current pricing is leaning on the absence of a decisive, airport-specific forecast rather than on any strong cold signal.

The main catalyst to watch is the next round of short-range updates for London City Airport itself, especially if high pressure strengthens or the warm spell persists through the morning peak. Wunderground’s hourly forecast for London already points to “very warm” conditions and a high of 83°F, which is materially above climatology, but the settlement source is the airport station and the market resolves off the recorded maximum rather than a citywide average[4]. If the forecast firms up in the next few hours, that would matter more than longer-range August climatology or broad regional outlooks, which the Met Office notes are only indicators of what is more likely, not day-to-day certainty[19].

Sources: 1 · 2 · 3 · 4 · 5

Methodology

This page tracks Highest temperature in London on August 3? across four political prediction venues. Live odds come from the Polymarket order book (the deepest political prediction-market book). Kalshi is the CFTC-regulated US alternative, Betfair the established UK sports-exchange with politics markets, Manifold the open play-money variant. For users geo-blocked from Polymarket directly, brokers like Election Predictions UK provide a 0%-fee route into the same order book.

Resolution & payout

Political markets typically settle on official candidate or agency confirmation. Polymarket uses UMA Optimistic Oracle: a proposer posts the outcome with a bond, the two-hour window opens, then the smart contract pays USDC.

Kalshi settles USD via CFTC clearinghouse, with clearly defined resolution sources (e.g. AP race calls for elections). Betfair settles after the official outcome is registered with the league or agency. Manifold is play-money.

FAQ

How accurate are political prediction markets?

Historically more accurate than polls. Polymarket's Brier score on US 2024 elections was ~0.11 — better than 538 (~0.14) and every mainstream poll. Markets aggregate information with real skin in the game.

What resolution source is used for elections?

Polymarket defines the source per contract — usually Associated Press (AP Race Call), Reuters or the official electoral commission. The source is stated in contract details before the market opens.

Which platform has the deepest political liquidity?

Polymarket — by far. US 2024 presidential volume was ~$3.5B vs Kalshi (~$200M) and Betfair (~$120M). Where Polymarket is geo-blocked, brokers like Election Predictions UK route into the same order book at 0% fees.

How fast do political markets react to news?

High-liquidity markets move within seconds to minutes. A Trump tweet on the economy can shift the "Trump 2024" market 2-5 points before mainstream media has written anything.

Why do Polymarket and Kalshi differ on elections?

Kalshi must follow CFTC compliance — strict definitions, clear resolution sources, US citizens only with KYC. Polymarket operates globally without CFTC oversight — deeper liquidity, but also higher regulatory risk.