Highest temperature in Helsinki on July 4?

Platform comparison

Market context

The real-world event hinges on whether Helsinki Vantaa Airport records a temperature exceeding the market’s threshold on 4 July 2026, with the crowd currently assigning zero probability to the “YES” outcome. This implies the consensus believes the day will be too cool to trigger the resolution, likely due to early-month variability or a lack of sustained heat. Yet, historical patterns suggest this view may be overly cautious. July in Finland has recently ended with record-breaking heatwaves pushing temperatures above 30°C, and the warmest day of July 2026 in Helsinki reached 22.6°C on 28 July, while the coldest dipped to 13.4°C on 2 July [1][2]. Early July often shows volatility, but the month’s overall warmth—averaging highs near 71°F at Vantaa—means a sudden spike is not impossible, especially if a late heatwave arrives unexpectedly [3].

Traders should monitor incoming weather forecasts for the Baltic region, particularly any announcements of high-pressure systems moving from the east, which could trigger rapid temperature rises. A recent forecast from AccuWeather indicates daily highs in Helsinki Vantaa Airport for July 2026 ranging between 65°F and 74°F, with overnight lows between 46°F and 58°F, suggesting the potential for a 74°F (23.3°C) peak if conditions align [5]. The key catalyst is the timing of any heatwave: if one arrives before 4 July, the value spot may lie in the contrarian angle that the market has underpriced the risk of an early surge. Wunderground’s historical data will be the definitive source, so real-time updates from that platform are critical [1]. Given the crowd-implied 0% probability, any credible forecast hinting at temperatures above the threshold could represent significant value for those willing to bet against the consensus.

Sources: 1 · 2 · 3 · 4 · 5

Methodology

This page is a comparison snapshot: one live quote, four reference venues with their key attributes, and a single execution path — every trade button routes to Who Will Win 2026, which mirrors the Polymarket order book directly.

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.

FAQ

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.

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.

How reliable are the quoted odds?

The YES/NO percentages are the live mid-prices of the Polymarket order book. On deep markets they move every few seconds; on thinner ones you'll see short plateaus.