Highest temperature in Hong Kong on May 21?

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Market context

Hong Kong’s highest temperature on 21 May is a straightforward weather print, and Polymarket is pricing the contract at 0% YES on USDC-settled conditional tokens on Polygon. With the settlement window ending at 2026-05-21T12:00:00Z, the market is effectively waiting on the Hong Kong Observatory’s final “Daily Extract” entry for the absolute daily maximum temperature, measured in Celsius.

For context, May in Hong Kong is already a warm month rather than a cool shoulder season. AccuWeather’s May outlook shows highs commonly around 83°F to 94°F, while WeatherSpark puts typical May daily highs in the low-to-mid 80s Fahrenheit, with the warmest stretch often in the final third of the month. The Hong Kong Observatory’s own past data underline that late May can deliver much hotter readings: May 2025 reached 33.0°C, and the month was notably warmer and drier than normal. That makes a high in the upper 20s or low 30s Celsius plausible, even if the exact outcome on 21 May remains dependent on local conditions.

Traders should watch the Observatory’s daily update cycle rather than headline forecasts alone. The market resolves only when the relevant daily extract is finalised, so any revision in the official record matters more than intraday weather chatter. Recent Observatory reporting also shows how quickly Hong Kong can swing into hot conditions; in 2025 the city logged 53 very hot days and 54 hot nights, both near record territory, according to the HKO and coverage from Earth.Org. In practice, the key dependency is whether 21 May lands under a stable subtropical ridge or a more unsettled, rain-cooled regime, since that will determine the maximum temperature that appears in the official record.

Sources: 1 · 2 · 3 · 4 · 5

Methodology

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FAQ

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