Seoul Overnight Low June 19: Will 20°C Hold?

Seoul’s overnight temperature markets have a short fuse. By midnight Korean Standard Time on June 19, this contract resolves — and the 20°C outcome currently trades at 54%, up sharply from 35% just 24 hours ago. That 19-percentage-point move in a single day is the real story here. Something shifted the market’s conviction fast, and the most likely driver is updated short-range forecast data from the Korea Meteorological Administration.

The market question is straightforward: what will Seoul’s lowest recorded temperature be on June 19, 2026? The contract resolves at 12:00 KST. The YES price sits at 0.54 and the NO price at 0.46, with total volume at $6,619 and 24-hour volume at $5,216 — meaning most of the money entered this market in the last day alone.

How the Contract Works: Seoul’s Minimum Temperature Threshold

This is an outright outcome market. The 20°C bucket pays out only if Seoul’s official minimum temperature on June 19 lands exactly at 20°C (or within the bin’s rounding range). The Korea Meteorological Administration records the official low at Jongno-gu station, the primary Seoul observing point. Multiple competing outcomes trade simultaneously: 19°C at its own price, 21°C at its own price, and a full ladder from 15°C or below up to 25°C or higher.

• YES (20°C outcome) trades at 0.54, implying a 54% probability that Seoul’s overnight low falls in the 20°C bin.
• NO (all other outcomes combined) trades at 0.46, implying a 46% probability that the low lands anywhere else on the ladder.

The NO side pays out if Seoul’s minimum temperature registers at 19°C, 21°C, or any other outcome on the ladder. June in Seoul sits in the pre-monsoon transition. The city’s average low in mid-June runs between 17°C and 21°C depending on cloud cover, southerly flow, and overnight humidity. A swing of two degrees in either direction is entirely plausible within a single forecast cycle, which is exactly why the NO side still holds 46%.

Sponsored Partner

Momentum and Market Signals: A Single-Day Surge

The momentum composite here is unambiguous. The 24-hour price change of plus 15% combined with a trend score of 55.87 and no movement in the last hour points to a market that absorbed new information yesterday and is now holding its position. The most logical catalyst is a KMA short-range forecast update narrowing the expected low toward 20°C for the overnight period.

Total volume of $6,619 is thin. The 24-hour volume of $5,216 represents nearly 79% of all money ever traded in this contract — a sign that liquidity entered fast and recently. The order book shows $48,403 in liquidity, which is deep relative to trading volume. That depth means a single new trade won’t crater the price, but it also means the current 54% reflects a small number of participants. Thin volume means price can move sharply on any new forecast data released before resolution.

• The 24-hour price change of plus 15% is the dominant signal, not the flat 1-hour reading — the market absorbed the catalyst and stabilized.
• The trend score of 55.87 sits just above neutral, consistent with a market that moved decisively but hasn’t reached high-conviction territory.
• Liquidity at $48,403 is unusually deep relative to total volume, suggesting a market maker or early participant seeded the order book before trading picked up.
• Related markets showing Seoul weather correlation are absent from the listed comparables, so no external cross-market signal is available to confirm direction.
• The 15-point jump from 35% to 54% within 24 hours is the sharpest signal in this dataset — it reflects a real forecast update, not noise.

Lines Analysis: What the KMA Forecast Is Saying

The KMA’s short-range models for June 19 are the only thing that matters here. Seoul’s June overnight lows are driven primarily by cloud cover trapping daytime heat and southwesterly monsoon-adjacent flow keeping moisture in the boundary layer. When those conditions align, the city’s minimum stays in the 19°C to 21°C band. The 54% probability on 20°C suggests the current model consensus is landing the overnight low squarely in that range — not a clean 19°C, not a 21°C.

What makes the NO side real is forecast uncertainty at the margins. If a clearer night develops — stronger radiative cooling, drier air from a brief northerly push — Seoul’s low could slip to 19°C or below. If cloud cover persists and southerly flow strengthens ahead of the monsoon onset, the low could stay at 21°C or edge higher. Both scenarios are plausible in the 12 to 24 hours before resolution. The KMA updates its official short-range guidance multiple times daily, and any shift in the overnight temperature forecast would reprice this contract immediately.

• A KMA forecast update showing the overnight low trending toward 19°C would push NO probability higher and deflate the 20°C outcome.
• Confirmation of persistent low-level cloud cover in Seoul for the overnight hours would support the 20°C outcome holding.
• A shift toward clearer skies and lower dewpoints in the next KMA model run would favor a 19°C resolution.
• Any significant precipitation or frontal passage before midnight KST would complicate the low temperature picture entirely.
• The final KMA bulletin issued on the evening of June 18 KST is the most important single data point before resolution.

Total volume of $6,619 is thin for a binary weather market. The data currently favors the 20°C outcome, but the margin is narrow and the measurement is inherently single-point and time-specific. One forecast model run separates 54% from 40%.

LINES VERDICT

NARROW LEAN TO YES

The 19-point surge in 24 hours reflects real forecast information, not sentiment drift. The KMA model consensus appears to have converged on 20°C for Seoul’s overnight low, and the order book depth suggests that positioning is holding.

What the market says: At 54%, the market is treating 20°C as the most likely single outcome but acknowledging that the full ladder of alternatives — from 19°C to 21°C and beyond — collectively represents a real competing probability. With resolution less than 24 hours away, any model update could shift pricing sharply.

Key unknown: The KMA’s final short-range temperature forecast for Seoul issued on the evening of June 18 KST is the single data point that will determine whether 20°C holds or the probability redistributes across the adjacent outcomes.

Scientific Context: Seoul’s June Temperature Climatology

Seoul’s mid-June climate sits at the edge of the East Asian monsoon onset window. The city’s average minimum temperature for June 19 historically ranges between 17°C and 21°C, with the specific value highly sensitive to cloud cover, dewpoint, and the timing of the Changma front. The 20°C outcome is climatologically central — it sits at the median of the expected range, which is why the market landed there after incorporating the latest forecast data. Outcomes at 22°C or above would require anomalous southerly advection. Outcomes at 18°C or below would require anomalous clear-sky radiative cooling. Neither is impossible in mid-June Seoul, but both require specific synoptic conditions that the current forecast does not appear to support.