Wellington May 31 High Temp: 18C at 66%

Wellington’s weather prediction market has moved fast. The 18°C outcome for May 31 sits at 66% implied probability, up more than 21 percentage points in the last 24 hours. That kind of momentum in a 48-hour weather market is a signal worth taking seriously.

The market question is simple: what will the highest temperature in Wellington be on May 31, 2026? The YES price for 18°C stands at $0.66. The NO price sits at $0.34. The market resolves at 12:00 UTC on May 31, 2026. Total volume has reached $48,199, with $41,138 traded in the last 24 hours alone.

How the 18°C Contract Works

This contract resolves YES if Wellington’s official high temperature on May 31 hits exactly 18°C. Resolution is determined by official temperature records for Wellington. Competing outcomes include 17°C, 19°C, 20°C, 21°C or higher, and several cooler options down to 11°C or below. Only one outcome pays out.

• YES (18°C): $0.66 per share, implying a 66% probability that Wellington’s high on May 31 lands at exactly 18°C.
• NO (any other temperature): $0.34 per share, covering the remaining 34% probability spread across 11 other outcome brackets.

The NO side pays when Wellington’s actual high misses the 18°C mark entirely, landing anywhere from 11°C or below up to 21°C or higher. Late May in Wellington sits firmly in autumn. The city’s historical autumn highs cluster in the 14°C to 18°C range, which means both warmer and cooler outcomes remain live. A frontal system pushing through the Cook Strait or a calm high-pressure day each shift the distribution meaningfully.

Momentum and Market Signals

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The combined momentum signal here is unusually strong for a local weather market. The 18°C contract gained 15% in the last hour and 21.5% over 24 hours. The trend score of 78.50 out of 100 confirms directional conviction. The most likely driver is updated short-range forecast data. Numerical weather prediction models for Wellington typically sharpen within 48 to 72 hours of the target date, and traders appear to be responding to model output pointing toward an 18°C high.

Total volume of $48,199 is thin by prediction market standards. With $41,138 of that arriving in the last 24 hours, liquidity of $115,849 is actually the deepest part of this market right now. Volume below $1M means price can move sharply on any new information, including a single updated forecast run or a change in synoptic pattern. The market is pricing uncertainty, not science.

• The 18°C YES contract gained 15.0% in the last hour and 21.5% over 24 hours, reflecting sharp model-driven repricing as resolution approaches.
• Liquidity at $115,849 exceeds 24-hour volume, which suggests the order book can absorb moderate new positions without extreme slippage.
• Total volume of $48,199 is low enough that a single large trade could move the YES price by several percentage points.
• The trend score of 78.50 places this contract in the upper quartile of directional momentum for science markets on this platform.
• No whale trades are recorded, which means the price movement reflects broad retail-level repricing rather than a single large directional bet.

Lines Analysis: Wellington Autumn Temperature Dynamics

Wellington’s geography drives its temperature volatility. The city sits at the southern tip of the North Island, directly exposed to Cook Strait wind patterns. Autumn highs in late May are heavily influenced by whether a blocking high sits over the Tasman Sea or a Southern Ocean trough tracks across the South Island. When the pattern is calm and northerly, highs reach 17°C to 19°C. When a frontal system arrives, highs can drop to 13°C or 14°C within hours. The current market price of 66% for exactly 18°C reflects a scenario where models are converging on a mild, settled day.

The case against 18°C is real. Wellington’s high landing at exactly 18°C requires the forecast to be right not just directionally but precisely. A day that runs 0.5°C warmer or cooler than the model median could resolve at 17°C or 19°C instead. Both of those outcomes sit in the market as separate contracts. Traders pricing YES on 18°C are essentially betting on forecast precision, not just forecast direction.

• MetService Wellington forecast updates within the next 12 hours could sharpen or shift the model consensus significantly.
• A change in wind direction from northerly to southerly would push the expected high below 17°C, collapsing the 18°C contract.
• A stronger-than-expected blocking high over the Tasman could push the high to 19°C or 20°C, also resolving NO for this contract.
• The 19°C and 20°C contracts on the same market represent live alternatives worth monitoring for relative price movements.
• Early morning temperature on May 31 will constrain the afternoon high range and serve as a real-time signal for traders holding positions.

Here’s what the measurements are telling us: the market repriced sharply because short-range forecast data narrowed the probability distribution toward 18°C. Total volume of $48,199 remains thin. The data slightly favors the YES side right now, but a single model update in the next 12 hours could shift that distribution. The data doesn’t care about the politics, and Wellington’s autumn weather doesn’t care about the market price.

LINES VERDICT

Narrow Forecast Consensus

The 18°C outcome has real momentum and short-range model support, but the YES contract is pricing on precision, not just direction. A one-degree miss in either direction resolves this NO.

What the market says: At 66% implied probability, the market has reasonable conviction that Wellington hits exactly 18°C on May 31, but with resolution in less than 24 hours and thin volume, a single forecast update carries enough weight to reprice this contract by 10 percentage points or more.

Key unknown: The next MetService model run for Wellington on the evening of May 30 is the single most important data point. If that run tightens the high forecast to 18°C with low uncertainty, the YES contract likely pushes above 70%. If it shifts to 17°C or 19°C, expect a sharp reversal.

Scientific Context: Wellington Late May Climatology

Wellington’s late May climate sits in the heart of the Southern Hemisphere autumn transition. Mean daily highs in May average around 14°C to 15°C, but individual days can vary by 5°C or more depending on synoptic pattern. The 18°C bracket sits at the warm end of the climatological distribution for this time of year. A northerly flow regime makes 18°C achievable. A southerly change makes it unlikely. Market pricing at 66% implies traders believe the current synoptic setup favors the warmer end of the range. The price will track forecast model output closely through the morning of May 31 until the actual observation closes the market.

What would move the price before May 31: Any MetService bulletin indicating a frontal trough approaching Wellington, any shift in the GFS or ECMWF model ensemble toward cooler or warmer outcomes, or any early May 31 temperature observation that constrains the afternoon high range.

How likely is this market to reach 18°C?

The current implied probability is 66%. That means the market assigns roughly two-in-three odds that Wellington’s official May 31 high lands at exactly 18°C, based on current forecast data and trader positioning.

What does the NO contract represent?

The NO side covers every outcome except exactly 18°C, including 17°C, 19°C, 20°C, 21°C or higher, and all cooler brackets. At $0.34, NO pays out if Wellington’s high misses 18°C in any direction.

What would move this market’s price the most?

An updated MetService short-range forecast shifting the expected high by one degree is the single highest-impact event. Thin volume means any model-driven repricing by active traders could move the YES price by 5 to 15 percentage points rapidly.

When does this market resolve?

The market resolves at 12:00 UTC on May 31, 2026. Resolution is based on official temperature records for Wellington covering the full day up to that point.

Is the volume reliable enough to trust this price?

Total volume of $48,199 is low. Liquidity of $115,849 provides some order book depth, but the thin volume means the 66% price reflects a relatively small number of trades. New information can move this price sharply.