Seattle in mid-May typically transitions from cool spring to early summer, with highs in the low to mid-50s Fahrenheit. A high of 48-49°F would be unusually cold for this time of year, representing a significant deviation from normal seasonal patterns. The market resolves based on the National Weather Service's official high temperature recorded at Seattle-Tacoma International Airport on May 18, 2026. Such a precise, narrow 1-degree range is inherently unlikely—weather systems rarely produce exact outcomes, and natural temperature variation typically spans 3-5 degrees around a given forecast high. The current 1% odds reflect trader consensus that this outcome is a tail event, requiring an unseasonable cold front, unexpected weather system, or other anomalous conditions. Historical May data for Seattle shows daily highs rarely fall below 50°F once spring is established; reaching only 48-49°F would signal either an unusually persistent cool pattern or a sudden Arctic intrusion late in the month. The extremely low price suggests most traders expect normal seasonal warming to continue, pushing the high into the 50s or above. Price trajectory and trading volume will likely remain minimal given the event's imminence and the tail-risk nature of the prediction.
Deep dive — what moves this market
Seattle's late-spring weather is shaped by the collision of retreating winter systems and advancing Pacific high-pressure ridges that drive the summer dry season. By mid-May, the city has typically experienced a month of gradually warming temperatures, with average highs climbing from the high 40s in early May to the mid-50s by month's end. A high of only 48-49°F would be a marked reversion, suggesting either an unusually slow warming trend or an unexpected intrusion of cold air. Such conditions could arise from several mechanisms: a late-season trough of low pressure bringing moisture and cool maritime air from the Pacific, a rare Arctic cold front penetrating far south, or a persistent upper-level pattern that continues to favor cool marine flow over the region. Historically, Seattle does occasionally experience cool May days—the record low high for May 18 is in the mid-40s—but days falling into the 48-49°F range occur infrequently and often represent statistical outliers rather than the rule. The NO case rests on robust seasonal climatology: Seattle has experienced strong warming by mid-May for decades, with late-May highs typically 10+ degrees above this narrow range. Modern climate patterns favor warm spells in May, and the typical progression by May 18 sees highs in the low-to-mid 50s with rising trends. A return to near-50°F temperatures would require disruption to the normal seasonal pattern—specifically, either a weather system stalling or redeveloping, or the persistence of cool maritime influence that should have weakened by this date. The 1% odds reflect this climatic reality: traders view this outcome as sufficiently improbable that it commands extreme pricing. The YES case requires specific meteorological conditions: a strong upper-level trough, sustained low-level marine air, and reduced solar heating combined with cloudiness. Such a pattern would be noteworthy but not unprecedented. Cool May days in Seattle have occurred; the question is whether the high will land precisely in this 1-degree window rather than in the broader 45-52°F range that cool May systems typically produce. The narrowness of the range is the key constraint—predicting a 48-49°F high is far more difficult than predicting "below 52°F" or "cool spring weather." For traders, the 1% price incorporates both the improbability of an unseasonable cool-down and the razor-thin margin of the 1-degree window. Even if cooler weather does materialize, landing exactly on 48-49°F demands precision from both the weather system and the official measurement.
What traders watch for
NWS Seattle 48-hour forecast issued May 17 evening; track predicted high temperature for market correlation.
Official NWS Seattle temperature reading released May 19 morning; check rounding rules for 48-49°F threshold.
Real-time hourly temperatures May 18 afternoon; critical hours 2pm-5pm determine if high stays below 50°F.
Cloud cover and wind patterns May 18 morning; persistent marine air and overcast skies support cool outcome.
How does this market resolve?
The market resolves YES if the National Weather Service Seattle office records an official high temperature of 48°F or 49°F on May 18, 2026. Resolution depends on the precise NWS measurement.
Prediction markets aggregate trader expectations into real-time probability estimates. On Polymarket Trade, every market question resolves YES or NO based on a specific event outcome; traders buy shares of the side they believe will resolve positively. Prices range 0¢ (certain no) to 100¢ (certain yes) and naturally reflect the crowd-implied probability of YES. This page summarizes the market state for readers arriving from search; for live trading (place orders, see order book depth, execute a trade) open the full interactive page linked above.
