Seattle High Temp May 19: Will It Hit 58°F?

Seattle’s high temperature forecast for May 19 has already been priced as a near-certainty. The contract on 58°F or higher sits at 97.5% probability, with essentially no momentum shift in the past 24 hours. The market has looked at the forecast and reached a verdict.

Here’s what the measurements are telling us: Pacific Northwest temperatures in mid-May regularly clear 58°F, and the current regional weather pattern supports a mild to warm afternoon across the Puget Sound lowlands. Thin liquidity means a surprise forecast revision could reprice this contract quickly, but as of May 18, traders are treating this as done.

How the Contract Works: Seattle’s May 19 Temperature Threshold

This contract resolves YES if Seattle’s official high temperature on May 19, 2026 reaches 58°F or above. Resolution is based on official temperature measurement at the designated Seattle observation point. The contract closes at noon UTC on May 19, 2026, which corresponds to early morning Pacific time. The full range of alternative outcomes spans 39°F or below up through 58°F or higher, covering every 2-degree band in between.

• 58°F or higher (YES): 0.97 price, 97.5% implied probability
• 56-57°F: alternative outcome, low probability
• 54-55°F and below: alternative outcomes, very low probability

A cooler outcome pays if Seattle’s high falls below 58°F on May 19. The National Weather Service Seattle forecast office would need to be tracking a significant cold intrusion, marine push, or persistent low cloud deck that suppresses afternoon temperatures by several degrees relative to current expectations. That scenario is not supported by the current synoptic pattern, which is why the alternative outcomes command less than 3% of market probability combined.

Sponsored Partner

Momentum and Market Signals: Flat Price, High Conviction

The momentum composite across 1-hour change, 24-hour change, and trend score is essentially static. No new data has moved this contract in the past 24 hours. The market is waiting for May 19 to arrive, not for a fresh forecast signal.

Total volume sits at $8,551, which is thin by any prediction market standard. Liquidity of $94,371 is meaningfully larger than trading volume, which tells you the order book has depth but actual trading activity is minimal. Thin volume markets like this one can gap sharply on a surprise, so the 97.5% price is not immune to a fast reprice if the National Weather Service Seattle office issues an updated forecast showing a stronger marine push overnight.

• The 1-hour price change of +0.0% and 24-hour change of +0.0% confirm no catalyst has fired in recent trading.
• The trend score of 29.63 reflects stable, low-activity conditions rather than building momentum in either direction.
• Total volume of $8,551 against $94,371 in liquidity means order book depth far exceeds actual market participation.
• Thin volume flags that a single large trade or a forecast revision could move the price faster than in higher-volume markets.
• The 97.5% YES price reflects consensus around a settled near-term weather forecast, not long-term climate uncertainty.

Lines Analysis: What the Forecast Supports

Mid-May in Seattle historically produces high temperatures well above 58°F under ridging or neutral pressure patterns. The climatological average high for Seattle in the second half of May sits in the low-to-mid 60s Fahrenheit. That baseline alone puts the 58°F threshold comfortably in reach under most plausible scenarios for May 19.

The risk scenario centers on marine air. The Puget Sound region is exposed to cool, moist Pacific flow that can suppress afternoon highs sharply when a marine layer persists through the morning hours. If a surface trough deepens along the Washington coast overnight May 18, onshore flow could hold Seattle’s high in the mid-50s. That is the specific meteorological condition that would push traders toward the alternative outcome buckets. The National Weather Service Seattle area forecast discussion would flag that scenario explicitly.

• A National Weather Service Seattle forecast discussion showing inland push of marine air would reprice the below-58°F outcomes upward quickly.
• Any upper-level ridge building over the Pacific Northwest would reinforce the YES outcome and could push probability above 98%.
• Overnight temperature data from SeaTac Airport (KSEA) on the morning of May 19 would confirm whether marine influence is suppressing the warming curve.
• Regional pressure gradient data from the morning of May 19 would signal whether the Puget Sound convergence zone is positioned to affect central Seattle.

The $8,551 in trading volume suggests this market has not attracted significant speculative interest, likely because the outcome appears obvious. The data favors YES. The only real question is whether the marine layer cooperates on May 19 morning.

LINES VERDICT

Seattle Clears the Bar

The mid-May Seattle climatology and current pattern both point well above 58°F. The market is pricing a settled forecast, and the data supports that read.

What the market says: The 97.5% YES probability translates to near-certainty in prediction market terms. Thin volume of $8,551 means the price could shift fast if a forecast update lands before the May 19 noon UTC resolution.

Key unknown: An overnight marine push or coastal trough deepening before May 19 morning is the single event that would reprice this contract. A National Weather Service Seattle forecast discussion flagging that scenario would be the clearest early signal.

Frequently Asked Questions

• What does 97.5% probability mean here? It means traders are putting roughly 97 cents on the dollar that Seattle’s high on May 19 reaches 58°F or above. It is not a guarantee, but it reflects very high consensus around the current forecast.
• What pays out on the alternative outcomes? Any outcome below 58°F pays the corresponding bucket. The combined probability across all sub-58°F outcomes is less than 3%, reflecting how unlikely the market considers a cooler day.
• What data could move the price before resolution? A National Weather Service Seattle forecast update showing a marine push or below-normal temperature outlook for May 19 afternoon would be the clearest reprice trigger.
• When does this contract resolve? Resolution is set for May 19, 2026 at 12:00 UTC, which is early morning Pacific Daylight Time. The actual high temperature reading for May 19 would be confirmed later in the afternoon Pacific time.
• Is $8,551 in volume enough to trust the price signal? Thin volume means the 97.5% price reflects a small number of trades. The large liquidity pool of $94,371 provides order book depth, but low volume markets can gap sharply on unexpected news.

This analysis reflects market conditions as of 2026-05-18 22:18:38. Prediction market probabilities are volatile and shift as new data and regulatory decisions emerge, especially as the 2026-05-19 12:00:00 resolution date approaches. Lines.com does not accept bets or provide financial or gambling advice. All market outcomes are uncertain.