Highest temperature in Helsinki on July 4?

Platform comparison

Market context

The underlying event is the peak temperature recorded at Helsinki-Vantaa Airport on 4 July 2026, measured in degrees Celsius and sourced from Wunderground. With the crowd-implied probability for the current range sitting at 0%, the market suggests the outcome is statistically unlikely, yet historical data shows July highs in Helsinki regularly reach 20°C to 24°C (68°F–75°F), with the monthly average high at 21.5°C (71°F)[3]. AccuWeather’s July 2026 forecast for the airport indicates daily highs between 18°C and 24°C (65°F–74°F), meaning a 0% probability likely reflects a mismatch between the selected range and realistic seasonal extremes rather than an absence of heat[2].

Programmatically, a trader would script a bot to poll Wunderground’s hourly archive for EFHK at 12:00 UTC on 4 July, comparing the live maximum against the market’s resolution thresholds. Key catalysts include the Finnish Meteorological Institute’s daily updates, which currently show 17.1°C at 12:00 on 3 July with falling pressure and moderate winds, suggesting potential for overnight warming or cloud cover shifts that could alter the peak[6]. BBC Weather notes today’s forecast as 19°C (67°F) with northeasterly winds, a pattern that historically correlates with stable daytime highs near 20°C–22°C[1]. Traders should monitor real-time METAR data from the airport and Wunderground’s rolling updates, as sudden wind direction changes or humidity spikes can push the maximum temperature beyond expected ranges.

Sources: 1 · 2 · 3 · 4 · 5

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

Polymarket-based markets settle through the UMA Optimistic Oracle on Polygon. A proposer submits the outcome, a two-hour challenge window opens, and unchallenged proposals finalise the resolution. Payouts settle automatically in USDC the moment the result is final — no bookmaker, no delay.

Kalshi-based markets settle in USD via the CFTC-regulated clearinghouse. Betfair Exchange settles in GBP/EUR net of commission. Manifold is play-money and does not pay out real funds.

FAQ

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 Bot UK. Kalshi charges up to 7% per trade; Betfair Exchange takes 2-5% commission on net winnings.

How does resolution work?

Through the UMA Optimistic Oracle on Polygon: a proposer submits the outcome, a two-hour challenge window opens, and USDC payouts settle automatically once the result is final.

What's the difference between YES and NO shares?

A YES share pays $1.00 if the event happens, $0 otherwise. A NO share pays $1.00 if the event doesn't happen. The market price between 0¢ and 100¢ is the implied probability.

What does Polymarket cost to trade?

Polymarket itself charges 0% — the only cost is the Polygon network fee, typically under $0.01 per transaction. Off-chain venues like Kalshi or Betfair charge 2-7% commission.

Do I need to KYC for this market?

On Polymarket directly, no — it's wallet-based. Intermediary brokers like Polymarket Bot UK trigger KYC only above $1,500 of lifetime trading volume; under that you trade pseudonymously with a single wallet address.