Highest temperature in Helsinki on July 4?

Platform comparison

Market context

The underlying real-world event is the highest temperature recorded at Helsinki-Vantaa Airport on 4 July 2026, with the Finnish Meteorological Institute forecasting a daytime high of 19°C and low model spread[2]. Historical data confirms July is typically Helsinki’s warmest month, averaging 21°C daytime highs, though recent years show variability, including a record-breaking heatwave ending July 2025 with temperatures above 30°C[1][3]. This context explains why the current crowd-implied probability of 0% for a specific range feels stark; while 19°C is plausible, the market may be pricing in the risk of a sudden spike or drop, given the region’s tendency for rapid weather shifts during summer[3][5].

Traders should monitor the 72-hour forecast updates from the Finnish Meteorological Institute, which currently project stable conditions but could shift with incoming Atlantic systems[2]. Key catalysts include any official announcements regarding heatwave warnings or precipitation schedules, as Helsinki averages six rainy days in July, which could suppress temperatures[3]. Recent news from the Climate Service highlights that July 2025 ended with a sweltering heatwave, suggesting that similar patterns could emerge in 2026 if atmospheric conditions align[1]. Additionally, on-chain mechanics on Polymarket—using USDC on Polygon with conditional tokens—mean liquidity and price movements will react instantly to these forecast updates, making timing critical for entry or exit[2].

Sources: 1 · 2 · 3 · 4 · 5

Methodology

We track Highest temperature in Helsinki on July 4? across the five venues with material prediction-market liquidity. The probability shown is the live Polymarket mid; the comparison rows summarise how each venue treats the underlying contract — fees, KYC thresholds, settlement currency, deposit options. The highlighted row marks the cheapest route into Polymarket's order book.

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

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.

How fast are USDC deposits?

Polygon credits deposits after 12 confirmations — usually under 30 seconds. Withdrawals follow the same path and land back in your wallet within minutes.

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.