This daily weather market tracks whether London's maximum temperature will reach 20°C (68°F) on May 17, 2026. The 0% YES odds signal overwhelming trader consensus that the high will fall short of this threshold, reflecting strong confidence in below-20°C conditions for the day. Mid-May in London typically sees daily highs ranging from 16–19°C, with substantial variability driven by Atlantic weather systems, sea surface temperatures, and jet stream positioning. A 20°C threshold represents a warm-but-not-exceptional May day for the region; the current market signal implies traders expect cooler-than-typical conditions, likely reflecting an anticipated cool Atlantic system or a persistent northwest flow pattern. The 0% pricing suggests near-certainty among traders that cooler conditions will dominate. Resolution depends on official Met Office temperature readings for London's central weather station, making this a direct and objectively verifiable outcome.
What factors could move this market?
London's May climate sits at a transition point between spring and early summer, when rapid warming can occur but Atlantic weather systems frequently drive temperature volatility. Historical data from the past two decades shows that May 17 highs in London rarely exceed 22°C and frequently fall between 16–19°C. The current market pricing at 0% YES—reflecting absolute trader conviction that the temperature will remain below 20°C—suggests a specific weather signal: either an established cool pattern already locked into forecasts, or a system expected to keep cooler Atlantic air in place through May 17.
Several factors could push toward a YES outcome. High pressure building from the south could draw warm continental air northward, a common recipe for rapid May warming in the UK. A shift toward southwesterly or southerly winds would pull warmer air masses into the region. Clear skies and solar heating in May, even with modest upper-level support, can drive highs toward 22–23°C on favorable days. Absence of rain-bearing systems would allow daytime heating to reach peak values. Recent years have seen May temperature records in the 25–28°C range for London, proving the potential for 20°C is routine.
Several factors work toward a NO outcome. The consistent 0% market pricing suggests traders see a strong weather signal: possibly a trough of low pressure, a vigorous Atlantic system, or a stubborn cool pattern that will persist through May 17. Northwesterly or northerly winds would transport cooler maritime air. An upper-level jet stream positioned to channel cool systems into the region rather than allowing warm air to penetrate would suppress temperatures. Persistent cloud cover or rain would suppress daytime highs. Sea surface temperatures around the UK in May average 12–14°C, and cooler-than-normal waters could suppress warming even with decent solar input.
The 0% odds imply traders have near-certainty about cooler conditions. This extreme conviction—no one is willing to pay even 1% odds for a 20°C outcome—suggests this market may have been seeded with traders holding strong directional conviction, or it reflects genuine consensus around a specific weather forecast signal. The $5.5K liquidity pool and $990 daily volume indicate this is a niche daily market without broad participation. Historically, London experiences 20°C+ days regularly in May (roughly 40% of May days exceed 20°C in a typical year), so the market's 0% stance represents confidence in an outlier outcome.
What are traders watching for?
Met Office forecast update on May 16–17 will clarify whether Atlantic systems remain entrenched or pressure patterns shift warmer.
Sea surface temperature anomalies and jet stream position determine whether warm continental air can penetrate or cool Atlantic flow persists.
Cloud cover and rainfall on May 17: persistent rain suppresses solar heating; clear skies maximize daytime warming potential.
Historical May 17 London highs (past 5 years) range 16–21°C; market's 0% implies expectation of lower-quartile outcome.
How does this market resolve?
Resolves YES if London's maximum temperature reaches 20°C or higher on May 17, 2026, per Met Office official readings. Market closes at 00:00 UTC on May 18.
Polymarket Trade is an independent third-party interface to the Polymarket CLOB prediction market exchange on Polygon — not affiliated with Polymarket, Inc. Prediction markets aggregate trader expectations into real-time probability estimates. Every market question resolves YES or NO based on a specific event outcome; traders buy shares of the side they believe will resolve positively. Prices range 0¢ (certain no) to 100¢ (certain yes) and naturally reflect the crowd-implied probability of YES. Polymarket Trade is non-custodial — your funds never leave your wallet. Open the full interactive page linked above to place orders, see order book depth, and execute a trade.
