San Francisco in mid-May typically experiences highs between 65-72°F, influenced by the Pacific's marine layer and coastal cooling patterns. The market asks whether the daily high will fall into an unusually narrow 60-61°F band on May 19, 2026 — a range representing cooler-than-typical conditions even for San Francisco's mild climate. At 1% YES odds, traders have priced this outcome as extremely unlikely, suggesting widespread confidence that May 19 will see temperatures either noticeably cooler or warmer than this specific window. The question is fully resolvable using National Weather Service official data for San Francisco International Airport or downtown monitoring stations, making it an objective, verifiable prediction. The 1% probability reflects the difficulty of hitting such a narrow meteorological target — weather systems would need to align specifically to keep conditions depressed to this range while avoiding both colder (below 60°F) and typical warmer (62°F+) outcomes. With only two days until resolution, this market has reached final pricing reflecting current atmospheric models and trader consensus about May 19's weather trajectory.
Deep dive — what moves this market
San Francisco's microclimate is shaped by the Pacific Ocean's cooling influence, marine layer fog that frequently blankets the city during spring, and local topography channeling winds through the Bay. May weather is transitional—spring giving way to early summer, with high variability driven by maritime and continental air mass interplay. Historically, May highs average around 67-70°F, though individual days swing from low 50s during strong marine layer events to high 70s on rare warm inland-flow days. The 60-61°F band sits at the lower-middle range of typical May variability. For YES resolution, specific conditions must align: a high-pressure system stalled over the Pacific maintaining vigorous marine layer throughout the day, cold northwesterly winds channeling through the Golden Gate, or an upper-level trough bringing cooler air aloft that resists daytime warming. Conversely, NO factors are far more abundant: inland warming beyond the marine layer, upper ridging allowing solar heating to exceed oceanic cooling, southwesterly flow bringing warmer air, or afternoon wind shifts breaking coastal clouds and spiking temperatures. Historical records show San Francisco rarely sustains one-degree temperature windows—weather systems typically drive 5-10°F swings rather than settle precisely at narrow bands. Recent spring patterns across the Bay have leaned toward moderate-to-warm May outcomes as climate has shifted, making specifically cool days increasingly uncommon. The 1% pricing reflects not just statistical improbability but the market's assessment that May 19 diverges significantly from the 60-61°F band. Traders holding contrarian YES positions bet against both consensus and atmospheric models—a challenging position. Thin liquidity ($2603) and minimal 24-hour volume ($9) suggest this is a specialist weather-prediction niche, meaning quoted odds reflect informed opinion from traders familiar with San Francisco micrometeorology.
What traders watch for
NWS official high temperature for San Francisco on May 19 at midnight UTC — sole resolution criterion.
Marine layer persistence and timing — whether clouds break or hold into afternoon, affecting temperature ceiling.
Wind pattern on May 19 — persistent onshore flow versus inland/offshore shift determines ocean cooling effectiveness.
Atmospheric setup May 16-18 — antecedent conditions and trough/ridge positioning influencing May 19 outcome.
Afternoon solar heating rate — cloud cover density and timing of any clearing that pushes temperatures above 61°F.
How does this market resolve?
Market resolves YES if San Francisco's official high temperature on May 19, 2026, is between 60.0°F and 61.9°F inclusive. Resolution uses NWS data for San Francisco International Airport at midnight UTC on May 20, 2026.
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.
