Seattle’s June 21 High: Will 78-79°F Hold?

Seattle’s prediction market for June 21 temperature just moved sharply. The 78-79°F bracket surged roughly thirty-three percentage points in the past hour, jumping from a coin-flip to the clear market leader. That kind of move almost never happens without a forecast update from the National Weather Service. The market is now pricing 77.5% confidence that Seattle’s highest temperature tomorrow lands in a two-degree band.

The market question asks: what is the highest temperature in Seattle on June 21, 2026? The 78-79°F bracket carries a YES price of $0.78 against a NO price of $0.23. The market resolves June 21 at 12:00. Total volume stands at $9,707, all of it traded in the last 24 hours.

How the Seattle Temperature Contract Works

This contract resolves YES if the official high temperature recorded in Seattle on June 21 falls between 78°F and 79°F inclusive. The National Weather Service Seattle office measures at Seattle-Tacoma International Airport, the standard official observation point. All other temperature brackets remain separate contracts trading simultaneously.

• YES pays out if the NWS-recorded daily high on June 21 hits 78°F or 79°F: currently priced at $0.78 (77.5% implied probability).
• NO pays out if the recorded high lands in any other temperature bracket: currently priced at $0.23 (22.5% implied probability).

The NO position wins if the Seattle high misses the 78-79°F window entirely, landing cooler or warmer. The competing brackets show the shape of uncertainty: 76-77°F and 80-81°F are the next most likely alternatives. Forecasts have tight margins, and a degree or two of model error is enough to flip this market.

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Momentum and Market Signals

The momentum signal here is unusually clean. A 33.5% price jump in one hour, combined with a trend score of 84.63, almost certainly reflects a fresh NWS forecast run or model consensus landing squarely on the 78-79°F range. Weather prediction markets move on exactly this kind of near-term forecast convergence. June 21 is the summer solstice, Seattle’s longest day, which adds solar-input context to any above-normal temperature call.

Total volume and 24-hour volume both sit at $9,707. Liquidity is deeper at $35,427, meaning the order book can absorb moderate additional trading without wild price swings. The volume level is below $10 million, so this is a thin market. One large position in any adjacent bracket could move prices noticeably before resolution tomorrow.

• The 1-hour price change of +33.5% signals a near-certain forecast model update pushing traders into the 78-79°F bracket.
• The trend score of 84.63 reflects strong directional conviction, not just noise.
• Liquidity of $35,427 provides some buffer, but the thin $9,707 volume means this market can reprice sharply on any new NWS advisory.
• The 24-hour volume matches total volume, confirming this market opened and moved entirely within one trading session.
• Adjacent brackets (76-77°F and 80-81°F) are the primary competing outcomes and will absorb capital if the forecast shifts even slightly.

Lines Analysis: The NWS Forecast and What Can Go Wrong

The 78-79°F bracket leads because recent forecast models have converged on that range for Seattle’s June 21 high. Seattle’s average late-June high sits around 72-75°F, so a reading in the 78-79°F band represents an above-normal but entirely plausible warm day, not an extreme event. The summer solstice adds peak solar forcing. Here’s what the measurements are telling us: the atmosphere and the models agree, and the market followed.

The 76-77°F bracket and the 80-81°F bracket represent the realistic risk scenarios. Temperature forecasts for Seattle carry inherent uncertainty even 24 hours out, because marine influence from Puget Sound and the Pacific can pull the high down, while inland heat can push it up. A marine push cooling the afternoon by two degrees moves this market to NO. A warm spell holding longer than forecast pushes it toward 80-81°F, also a NO outcome for this bracket.

• A fresh NWS afternoon forecast discussion confirming 78-79°F would push YES toward 85-90%.
• A revised NWS forecast dropping the predicted high to 76-77°F would immediately collapse YES pricing.
• Marine layer intrusion in the morning is Seattle’s most common mechanism for afternoon high-temperature misses in late June.
• Strong easterly flow from the Cascades would push the high toward 80°F or above, benefiting the 80-81°F bracket instead.
• The 12:00 resolution time is worth watching: if the market resolves at noon local time rather than end of day, the true daily maximum may not yet have occurred, which is a structural risk for all bracket holders.

The data doesn’t care about the politics, and here the data is straightforward. The NWS forecast and market pricing align at 77.5%. Total volume of $9,707 is thin, and a single updated forecast advisory in the next 18 hours could move this meaningfully. The measurements favor YES, but the two-degree resolution window is narrow.

LINES VERDICT

FORECAST-CONFIRMED LEADER IN A NARROW WINDOW

The 78-79°F bracket holds the clearest signal in this market, supported by a sharp forecast-driven price move. The data favors YES, but the resolution window is only two degrees wide, and Seattle’s marine influence makes any forecast miss possible right up to the temperature peak.

What the market says: 77.5% probability that Seattle’s June 21 high lands in the 78-79°F bracket. The market is pricing uncertainty, not science, and with a resolution date of June 21 at 12:00, this contract will settle within hours.

Key unknown: The next NWS Seattle forecast advisory, expected before tomorrow morning, will either confirm or revise the 78-79°F target. That single update is the most important repricing event before resolution.

Scientific Context: Seattle Temperature Forecasting

Seattle’s temperature regime in late June is shaped by two competing forces: Pacific marine influence pushing cool, moist air inland, and continental heat building over eastern Washington. The summer solstice maximizes daylight hours, giving any warm airmass additional time to drive surface temperatures upward. Seattle-Tacoma International Airport sits at roughly 433 feet elevation, slightly removed from the immediate coast, making it more responsive to inland heat than downtown Seattle or waterfront stations. The NWS Seattle office issues area forecasts twice daily, with spot forecasts updating more frequently. A two-degree bracket in a 24-hour temperature forecast sits at the edge of routine forecast confidence intervals for this region.