Seoul Low Temperature June 29: Will 21°C Hold?

Seoul’s overnight low on June 29 has become one of the sharpest short-term weather contracts on Polymarket this week. The market moved from a coin-flip territory to near-certainty in 24 hours, pricing 21°C as the most likely minimum temperature at an implied probability of 84.5%. That kind of momentum in a single day is not noise. It reflects real atmospheric data converging on a specific outcome with less than 24 hours to resolution.

The market question asks: what will the lowest temperature in Seoul be on June 29? The YES position at $0.85 covers 21°C. The NO position sits at $0.16. Total traded volume is $7,673, with $6,683 of that arriving in the last 24 hours. The market resolves at noon Seoul time on June 29, 2026.

How the 21°C Contract Works

This is a discrete temperature band contract. YES pays if Seoul’s official minimum temperature on June 29 lands at exactly 21°C. NO pays if the recorded low falls outside that band, whether higher or lower. Resolution follows the official meteorological reading, not a modeled estimate.

• YES ($0.85, ~84.5% probability): Seoul’s minimum temperature on June 29 is officially recorded at 21°C.
• NO ($0.16, ~15.5% probability): The low comes in at any other value, including 20°C, 22°C, or any adjacent band.

A NO outcome does not require a dramatic cold snap or heat surge. Late-season atmospheric variability in Seoul during late June can shift overnight lows by one or two degrees. The Korea Meteorological Administration publishes daily minimum readings, and that single number determines everything here. A reading of 20°C or 22°C is enough to flip the contract.

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Momentum and Market Signals

The momentum composite here is unusually strong for a 24-hour weather contract. The 1-hour change of +33.0% and 24-hour change of +40.5%, combined with a trend score of 83.68, point to a decisive repricing event. The most likely driver is updated numerical weather prediction output from late June 28, which would have incorporated the latest radiosonde and surface observation data for the Korean Peninsula. When short-range forecasting models converge on a specific overnight low, traders who track those outputs move quickly.

Total volume of $7,673 is thin. Volume under $1 million means this contract can reprice sharply on a single updated forecast or a late model run. Liquidity sits at $22,982, which provides some buffer, but a confident counter-position of even a few hundred dollars could shift the NO price meaningfully before resolution.

• The 24-hour volume of $6,683 represents roughly 87% of all trading activity, confirming this is a very recent conviction shift, not a slow build.
• The 1-hour and 24-hour price changes together suggest a triggering event, likely a model forecast update showing 21°C convergence across multiple weather prediction systems.
• Thin total volume means price is not anchored by deep market structure. A single large trade near resolution could move the market.
• The trend score of 83.68 places this contract in the upper tier of directional momentum on the platform as of June 28, 2026.
• The market opened at $0.54 and dropped to the mid-$0.40s before surging. That pattern suggests early uncertainty followed by a hard data signal.

Lines Analysis: Seoul’s Overnight Low and What the Data Favors

Late June in Seoul sits at the front edge of the East Asian monsoon season. The city’s overnight lows during this period typically range between 19°C and 24°C, depending on how far the Changma front has advanced and whether the urban heat island effect is modulated by cloud cover or rainfall. A 21°C minimum is entirely consistent with a partly cloudy, marginally humid night ahead of a monsoon boundary. The market’s rapid convergence on this number tracks with what short-range ensemble models tend to show when the atmospheric setup is relatively clean and the monsoon boundary is not directly overhead.

The 15.5% NO probability is not dismissible. Seoul’s official minimum temperature is sensitive to the exact timing of nocturnal cooling and any convective activity that passes through after midnight. A brief shower before dawn could suppress cooling and push the low toward 22°C or 23°C. A clearer-than-expected night could allow temperatures to dip to 20°C. The Korea Meteorological Administration’s automated surface observation network records these values at the Jongno or Seoul regional station, and the band precision means one degree of deviation resolves the contract against YES.

SIGNALS TO MONITOR

• Korea Meteorological Administration’s final 24-hour forecast for Seoul issued late June 28: if the predicted low shifts from 21°C to 20°C or 22°C, expect NO-side movement before resolution.
• GFS and ECMWF model agreement on the overnight low: strong model consensus on 21°C would further entrench the YES price near $0.90 or higher.
• Changma front position: if the front stalls directly over Seoul on the night of June 28-29, convective cloud cover could prevent nocturnal cooling below 21-22°C range.
• Surface wind direction: a southerly flow brings warmer, more humid air and suppresses cooling. A brief northerly shift could push the low toward 20°C.
• KMA automated station data published after midnight Seoul time: any early-hour reading approaching 20°C or 22°C would be the clearest real-time signal before noon resolution.

Total volume of $7,673 keeps this contract in speculative territory. The data flow favors YES, but thin markets with a single-degree resolution band carry structural risk that deeper markets absorb more easily. The 24-hour price action says traders who track meteorological model output have made their call. The question is whether the atmosphere agrees before the 12:00 Seoul deadline.

LINES VERDICT

NARROW CONVICTION, WEATHER-DEPENDENT

The market’s rapid repricing to 84.5% reflects genuine meteorological signal, not thin-air speculation. Seoul’s atmospheric setup for June 29 is consistent with a 21°C overnight low, and model convergence appears to be driving the YES surge.

What the market says: An implied probability of 84.5% translates to the market treating 21°C as the strong favorite, but not a certainty. With less than 24 hours to resolution and a single-degree band determining outcome, volatility risk remains elevated until the KMA publishes the official reading.

Key unknown: The Korea Meteorological Administration’s official minimum temperature reading for Seoul on June 29 is the single data point that resolves this contract. Any forecast shift showing the low at 20°C or 22°C before midnight Seoul time would be the clearest signal to reprice before resolution.