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Hong Kong in late May enters the warm season, with typical overnight lows in the mid-to-high 20s Celsius. A low of 21°C or below would represent unusually cool weather for this time of year, roughly 4–7 degrees below the seasonal average. The 1% market probability reflects high confidence that May 28 will see temperatures well above this threshold. Hong Kong's subtropical climate displays relatively stable weather patterns in May before the onset of the summer monsoon in June, with most nights hovering between 24–28°C. Current market odds suggest traders expect nearly certain warmth, backed by historical May temperature data. Light trading volume ($202 in 24 hours) and modest liquidity ($1,110) are typical for daily temperature contracts with narrow resolution windows and short timeframes.
What factors could move this market?
Hong Kong's climate during late May exists in a transitional zone between spring and full summer conditions. The city's subtropical maritime location, surrounded by the warm South China Sea, creates relatively stable temperature patterns with consistent warmth and high humidity. May is historically one of the drier months before the rainy season intensifies in June, but thermometers remain elevated due to accumulated solar radiation and warm ocean surface temperatures. A low of 21°C would represent an exceptionally rare occurrence—it would require an unusual weather system, either a strong cold front pushing south from mainland China or an upper-level circulation anomaly that draws cool air masses toward the region unexpectedly.
Historically, Hong Kong's May lows rarely dip below 22°C, and readings at or below 21°C are exceptionally uncommon in modern climate records. This rarity explains the 1% market odds: traders have decades of observational data showing such cool nights are nearly impossible during this season. The South China Sea's warm waters act as a heat reservoir, maintaining nighttime temperatures even when daytime fluctuations occur. For the low to reach 21°C or below on May 28, multiple atmospheric conditions would need to align—strong cold air advection, clear skies preventing radiative heat retention, and a low-pressure system pulling Arctic air southward, all contradictory to typical May weather patterns.
Conversely, the 99% odds favoring above 21°C reflect the climatic norm. May 28 sits late in spring when subtropical high-pressure systems strengthen and daytime highs regularly exceed 30°C, with lows settling into the 24–27°C range. Ocean temperatures have warmed significantly by this date, inhibiting any imported cold air from maintaining intensity. Recent years have seen more frequent heat records in Southeast Asia during May, not cold records, further reinforcing trader confidence. The market's crystallized odds suggest no remaining uncertainty—with only four days until resolution, trader consensus has solidified, leaving minimal room for new information to shift sentiment.
What are traders watching for?
Watch for cold fronts or upper-atmosphere circulation changes approaching Southeast Asia between May 24 and May 28
Monitor ocean surface temperature anomalies in the South China Sea that could influence nighttime cooling patterns
Track overnight low temperatures from May 26–27 as early indicators of broader weather patterns through May 28
Review Hong Kong Observatory weather alerts and forecasts for any unusual cold air advection events
How does this market resolve?
Market resolves YES if Hong Kong's lowest temperature on May 28, 2026 is 21°C or below, verified by Hong Kong Observatory official data. NO if the low exceeds 21°C.
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.
