Tokyo in late May is in full late spring, with typical minimum temperatures ranging from 15–18°C. A 12°C low is cooler than average but entirely plausible if a cold front pushes south from higher latitudes. The 5% YES odds reflect trader assessment that this is a tail-risk event—unlikely given normal seasonal patterns, but acknowledging the real possibility of an unseasonable cool day. The market is precisely resolvable through the Japan Meteorological Agency's daily temperature reports, which are publicly available and widely monitored. Historical records show Tokyo experiences minimum temperatures of 12°C or below on roughly 5–8% of May days in typical years, so the current price aligns with observed frequency. Traders pricing this at 5% are essentially betting on warmer-than-typical weather but respecting the historical tail probability.
Deep dive — what moves this market
Tokyo's weather is among the most reliably measured and transparently reported data points globally, making temperature markets ideal for precise settlement. The Japan Meteorological Agency publishes daily readings with high accuracy, eliminating ambiguity. Late May marks a critical transition in Tokyo's seasonal cycle—the city is typically warming steadily, with solar heating intensifying and sea-surface temperatures moderating nighttime lows. Average minimum temperatures sit in the 15–18°C band, but this baseline masks significant variability driven by synoptic weather patterns. Cold fronts occasionally descend from Siberia and Mongolia into East Asia, penetrating southward to affect Tokyo even in May. These systems can temporarily reverse warming trends, driving lows into the 10–14°C range through northerly winds and suppressed solar radiation. What catalysts could push outcomes toward YES? A high-amplitude trough in the jet stream stalling over Japan would be primary; such patterns correlate with broad Asian monsoon disruptions and high-latitude blocking. Cold low-pressure systems, persistent cloud cover, and anomalous northerly flow all increase likelihood. Conversely, normal seasonal progression is the strong baseline. Persistent high-pressure ridging (typical for May), urban heat island effects adding 1–2°C, and increasing solar radiation all support warmer nights. The thermal inertia of spring and ocean moderation make sustained cool spells unlikely. Historically, 12°C May lows in Tokyo cluster around early May (when spring is younger) rather than late May. The 5% current price reflects this robust seasonal backdrop—traders are anchoring to historical frequency while acknowledging that multi-decade warming trends may have shifted the tail probability even lower in recent years. The market's modest liquidity suggests pricing could shift meaningfully if weather models issued mid-May show unexpected cooling signals or jet stream anomalies.
What traders watch for
Monitor Japan Meteorological Agency 10-day forecasts from May 11–14 for any cold-front signals or unseasonable patterns moving into Tokyo.
Track upper-air jet stream position and any southward excursions over East Asia; northerly flow increases 12°C likelihood.
Watch for high-pressure ridging or low-pressure troughs; high pressure brings warm conditions, low pressure brings cooler air.
Compare long-range weather models (GFS, ECMwf) issued May 15–19; sudden cooling signals could shift market odds meaningfully.
Historical May records show Tokyo rarely drops below 12°C; monitor emerging forecasts as May 21 approaches to refine estimates.
How does this market resolve?
The market resolves YES if Tokyo's official minimum temperature on May 21, 2026 reaches exactly 12°C as reported by the Japan Meteorological Agency. Any temperature above or below 12°C resolves NO.
Prediction markets aggregate trader expectations into real-time probability estimates. On Polymarket Trade, 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. This page summarizes the market state for readers arriving from search; for live trading (place orders, see order book depth, execute a trade) open the full interactive page linked above.
