Highest temperature in Wellington on August 21?

Platform comparison

Market context

Wellington International Airport will record a maximum temperature on 21 August 2026, measured against the Daily Observations table on Weather Underground rather than the summary high-low figures. The settlement window closes at midday UTC on that date, meaning traders are pricing the likelihood of specific temperature thresholds being breached during the preceding 24 hours. Polymarket currently shows 0% implied probability across all temperature bands, suggesting either illiquidity in this contract or genuine uncertainty about which range will resolve.

August is Wellington's coldest month, with historical daily maxima typically ranging between 11°C and 14°C at the airport station. The 30-year mean maximum for mid-August sits around 12.5°C, though individual days frequently deviate by 2–3 degrees depending on wind patterns and frontal systems. Traders should reference the MetService historical data for Wellington Airport; the coldest August day on record reached 6°C, whilst warmer outliers have touched 19°C during nor'west föhn conditions. The 0% pricing likely reflects low trading volume rather than consensus that no temperature will be recorded.

The key variable is whether a significant weather system moves through the lower North Island in late August 2026. MetService's long-range forecasts become increasingly unreliable beyond two weeks, so traders should monitor the official forecast issued around 15 August. Nor'west wind events—which can push temperatures 5–8 degrees above seasonal norms—occur sporadically in Wellington's winter but remain difficult to predict months ahead. The resolution mechanism's reliance on Weather Underground's Daily Observations table rather than summary figures introduces minor technical risk; traders should verify the station's reporting status closer to the settlement date.

Methodology

Methodologically we separate two layers: the live probability (Polymarket mid-price) and the platform attributes (fee, KYC, settlement currency, payment rails). That keeps the comparison honest — a single canonical probability across the row, with the venue-by-venue trade-offs spelt out in the columns next to it.

Resolution & payout

At resolution the UMA oracle takes over: a proposer posts the outcome with a bond, any token holder can dispute within two hours. Without dispute the result is accepted and the smart contract distributes USDC instantly.

On Kalshi (CFTC-regulated) resolution runs through their in-house clearing engine in USD. Betfair Exchange settles after match end in the account's local currency. Manifold pays no cash — only its in-platform "mana" currency.

UK Frequently Asked Questions

Where can I trade this market with the lowest fees?

Polymarket is geo-blocked in the US/UK/EU. The easiest 0%-fee broker into the same order book is Polymarket Scam?. Kalshi charges up to 7% per trade; Betfair Exchange takes 2-5% commission on net winnings.

Is this market available outside the US?

Polymarket itself is geo-blocked in the US/UK/EU. Always check the legal status of prediction markets in your jurisdiction before trading.

Is Polymarket legal in the UK?

Polymarket is accessible to UK traders but is not UKGC-licensed. It operates under US CFTC jurisdiction. UK residents face no domestic legal prohibition on using it, but UKGC consumer protections do not apply. For UKGC-regulated alternatives, Betfair Exchange and Smarkets offer similar prediction-style markets.

Do I pay tax on prediction market profits in the UK?

UKGC-licensed platform profits (Betfair, Smarkets) are typically tax-free gambling winnings for UK individuals. Polymarket profits involve USDC crypto transactions, which HMRC treats as Capital Gains Tax events. Keep full transaction records and report via Self Assessment if gains exceed £3,000 per tax year.

How do I deposit on Polymarket from the UK?

UK traders typically fund Polymarket via Coinbase UK, Kraken or Revolut — buying USDC with GBP and transferring to a Polygon-compatible wallet (MetaMask, Coinbase Wallet). Polymarket's onboarding walks you through the bridging process. Typical GBP-to-USDC conversion costs 0.5–1%.