Hong Kong May 4 Low Temp: Will It Hit Twenty-One Degrees?

A 27.5% price surge in 24 hours is not normal behavior for a temperature market. The 21°C outcome for Hong Kong’s lowest temperature on May 4 has climbed from a long-shot position to the market leader, now sitting at 64% implied probability. That kind of momentum in a thin-liquidity market demands explanation before resolution at 2026-05-04 12:00:00.

The contract resolves on a single meteorological fact: what is the lowest temperature recorded in Hong Kong on May 4, 2026? The Hong Kong Observatory tracks this data continuously. Eleven possible outcomes are on the table, ranging from 15°C or below up to 25°C or higher. Right now, traders are betting 21°C is the number.

How the Twenty-One Degree Threshold Works

The contract pays out if the Hong Kong Observatory records 21°C as the day’s minimum temperature on May 4, 2026. The resolution source is the official measurement from that body. Every other outcome, from 20°C to 25°C or higher, returns nothing on this contract.

• YES (21°C): Priced at 0.64, implying a 64% probability that the Observatory records exactly 21°C as the day’s low.
• NO (not 21°C): Priced at 0.36, implying a 36% probability that the low falls on any other listed outcome.

The NO outcome covers every competing result. Hong Kong in early May typically sees overnight lows in the 20-24°C range as the city transitions from spring to its pre-typhoon humid season. A reading at 20°C, 22°C, or 23°C would all pay out against this contract. That is a wide basket of alternatives, which makes the 64% concentration on one specific degree notable.

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Momentum and Market Signals: One Day Did the Work

The 24-hour price change of +27.5%, the trend score of 61.39, and the flat 1-hour reading combine into a single signal: this market moved hard on May 3 and has since stabilized at the new level. The 1-hour flatness suggests the buying pressure that drove Thursday’s surge has paused, not reversed.

Total volume is $5,644. The 24-hour figure of $4,535 means roughly 80% of all trading activity happened in the last day alone. Liquidity stands at $33,208, which is the order book depth. Volume this far below $1M means this market can reprice sharply on a single trade or new weather forecast. The current 64% reading reflects thin conviction, not a deep consensus.

• The +27.5% 24-hour move on May 3 aligns with updated short-range weather forecasts for Hong Kong, which likely narrowed the probable overnight low range toward 21°C.
• The 1-hour change of +0.0% shows the market has found a temporary equilibrium at 0.64.
• The trend score of 61.39 confirms moderate bullish momentum, not an extreme reading.
• Liquidity at $33,208 against volume of $5,644 signals that large bets relative to current activity could move this price significantly before resolution.
• Open interest is $0, which limits the ability to read sustained directional conviction from position data.

Lines Analysis: What the Hong Kong Observatory Data Supports

Here’s what the measurements are telling us. Early May in Hong Kong historically produces overnight lows between 20°C and 23°C. The Hong Kong Observatory’s climatological record for this period shows 21°C falls squarely within the most common range. Southwesterly winds and residual marine moisture typically keep temperatures from dropping below 19°C in the city center. The synoptic pattern for May 4 would need to reflect that moderate overnight cooling, not a cold front or unusual wind shift, to confirm 21°C.

The NO side is real and wide. Twenty°C would require slightly stronger cooling, perhaps a brief northerly intrusion. Twenty-two°C or 23°C would suggest warmer marine air held overnight temperatures higher than forecast. Any of those outcomes collapses this contract. The Hong Kong Observatory’s hourly readings are the only data that matter at resolution. There is no appeals process, no adjusted reading, and no margin for rounding.

• The Hong Kong Observatory’s official temperature record for May 4, 2026 is the sole resolution trigger.
• A short-range forecast update on the evening of May 3 or early May 4 could shift trader positioning before the market closes.
• Any change in the synoptic weather pattern, such as a stronger-than-expected southwesterly surge or a brief northerly trough, would push the outcome toward adjacent temperature outcomes.
• Urban heat island effects in Hong Kong tend to keep overnight lows 1-2°C above surrounding rural stations, which supports the 21-22°C range for city-center Observatory readings.
• Resolution is at 2026-05-04 12:00:00, so any late overnight temperature drop before dawn on May 4 is fully captured in the contract.

The data favors the 21°C outcome within the current forecast window, but the $5,644 total volume means this is a market pricing a weather forecast, not a settled scientific consensus. The market is pricing uncertainty, not science.

LINES VERDICT

Narrow Forecast Alignment

The 21°C outcome holds a 64% edge because Hong Kong’s early-May climatology and current forecast models point to overnight lows in exactly this range. The 27.5% single-day move reflects a forecast update, not new scientific data.

What the market says: Sixty-four percent of current capital believes the Hong Kong Observatory will record exactly 21°C as the May 4 minimum. This is a thin-volume market. A single updated forecast or a weather model shift before 2026-05-04 12:00:00 could move the price sharply in either direction.

Key unknown: The Hong Kong Observatory’s final short-range temperature forecast issued on the evening of May 3 or early morning of May 4 is the single data point that would reprice this contract before resolution.

Scientific Context: Hong Kong Temperature Climatology

Hong Kong’s early May climate is shaped by the transition from the northeast monsoon to the southwest monsoon. The Hong Kong Observatory records overnight minimums that cluster between 20°C and 24°C during this period. The city’s maritime location and urban density compress the range of probable overnight lows, making 1-degree-resolution prediction markets unusually competitive. A 21°C reading sits at the cooler end of the typical May range, consistent with a moderate overnight sea breeze without sustained southwesterly warming. Before 2026-05-04 12:00:00, any new forecast data from the Hong Kong Observatory or regional numerical weather prediction models would be the primary price mover for this contract.

Frequently Asked Questions

• What does 64% probability mean here? It means current market participants believe there is roughly a 64-in-100 chance the Hong Kong Observatory records exactly 21°C as the May 4 minimum temperature. Prediction market probabilities shift as new weather forecast data becomes available.
• How does the NO contract pay out? The NO position (priced at 0.36) pays if the Hong Kong Observatory records any temperature other than 21°C as the day’s low. That includes 20°C, 22°C, 23°C, and all other listed outcomes.
• What data would move this market before resolution? An updated short-range weather forecast from the Hong Kong Observatory or regional weather models showing a shift in overnight low projections for May 4 would be the primary price catalyst.
• When does this contract resolve? Resolution is set for 2026-05-04 12:00:00. The Hong Kong Observatory’s official minimum temperature record for May 4, 2026 determines the outcome.
• Is volume reliable enough to trust this price? Total volume is $5,644, well below $1M. Liquidity stands at $33,208. Low volume means the current 64% probability can shift significantly on a small number of trades. Treat this price as a directional signal, not a precise probability estimate.

This analysis reflects market conditions as of 2026-05-03 14:11:47. Prediction market probabilities are volatile and shift as new data and regulatory decisions emerge, especially as the 2026-05-04 12:00:00 resolution date approaches. Lines.com does not accept bets or provide financial or gambling advice. All market outcomes are uncertain.