Seoul Temperature Forecast for July 20: Will It Hit 27°C or Higher?

What is happening now

The market centers on predicting Seoul’s highest temperature on July 20, 2026, using Wunderground’s historical data from Incheon Intl Airport Station. Current prices show extreme confidence in temperatures below 27°C, with the “21°C or below” market at 100% probability and “27°C” at 99.2%. However, the “27°C” market’s “Yes” outcome is priced at 0.9915, suggesting near-certainty of at least 27°C, creating a contradiction. This implies traders may be hedging or anticipating a narrow range between 27°C and 30°C, though the market structure complicates interpretation. No official temperature data exists yet, as resolution depends on post-July 20 Wunderground updates.

How the market is structured

This is a price-range ladder market with 11 binary outcomes (21°C or below, 22°C, 23°C, …, 31°C or higher). Each market resolves to “Yes” if the recorded temperature matches its threshold, “No” otherwise. The “27°C” market is the only one with a “Yes” price above 0.99 (0.9915), while all others below 27°C are at 100% “No” and those above 27°C are near 0%. The structure forces traders to bet on exact thresholds, creating overlapping probabilities that may not align with traditional temperature distributions.

Path to the leading outcome

For the “27°C” market to resolve as “Yes,” the highest temperature must be exactly 27°C. This requires:

• No readings above 27°C (e.g., 28°C, 29°C, or 30°C).
• At least one reading hitting 27°C during the day.

The “21°C or below” market’s 100% “No” price implies traders expect temperatures to exceed 21°C, likely clustering around 27°C based on current pricing.

What could change the pricing

Key risks include:

• Early data leaks: If Wunderground’s historical data for July 20, 2026, is prematurely published, it could shift prices. For example, a 28°C reading would collapse the “27°C” “Yes” market.
• Weather anomalies: Unusually high temperatures (e.g., 30°C+) would favor the “30°C” market, while cooler days would boost lower thresholds.
• Market arbitrage: The conflicting prices between “21°C or below” (100% “No”) and “27°C” (99.2% “Yes”) suggest potential mispricing. Traders might exploit this by shorting lower thresholds and buying “27°C” contracts.

Editorial read

The market’s structure creates inherent contradictions. While the “27°C” market is priced as near-certain, the “21°C or below” market’s 100% “No” implies temperatures will exceed 21°C, aligning with the “27°C” outcome. However, the absence of resolution data until after July 20 leaves room for surprises. High liquidity in the “27°C” and “28°C” markets ($100M+ volume) suggests active trading, but the lack of independent verification for Wunderground’s data introduces uncertainty. Traders betting on exact thresholds may face volatility if weather patterns deviate from expectations. The market’s design prioritizes speculative range betting over straightforward temperature prediction, amplifying risks for uninformed participants.