Highest temperature in London on May 20?

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Active sub-markets

Market context

The outcome will be set by the highest temperature recorded at London City Airport on 20 May, using the final Wunderground history for that station. With the market already resolved in practice, the relevant benchmark is the observed daily maximum rather than any forecast range. For context, London’s mid-May highs often sit in the high teens or low 20s Celsius, so a reading around 20°C is not unusual for the city in a settled spring spell.

Recent comparable cases show how quickly London temperatures can move when high pressure builds over southern England. The Met Office noted that parts of west Wales and south-east England moved above 20°C during a recent warm spell, while London itself has also been forecast into the mid-20s in stronger surges. That makes a threshold in the low 20s plausible on warmer days, but not the default outcome if cloud or a sea breeze limits heating.

The key catalyst for traders is the confirmed station observation, not polling or campaign-style movement. The market’s reference point is the London City Airport Met Office site as mirrored in Wunderground’s daily history, so any final change comes from the recorded maximum for the day once the data are fixed. For broader context on how warm the period can be, AccuWeather’s May outlook for London has pointed to highs in the low-to-mid 20s Celsius on some days, with averages below that, which underlines the dependence on day-specific conditions rather than the monthly norm.

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Methodology

Political prediction markets differ structurally from sports betting: thinner liquidity, longer settlement windows, higher sensitivity to single news events. This page shows the live Polymarket quote for Highest temperature in London on May 20? plus platform attributes for the three reference venues, so you can see at a glance where the deepest market for this question sits.

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

Is this market available outside the US?

PolyGram is available in most jurisdictions where Polymarket isn't directly accessible. Polymarket itself is geo-blocked in the US/UK/EU. Always check local regulations.

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.

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, PolyGram 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.