San Francisco's May weather is notoriously volatile, shaped by the Pacific Ocean's cool influence, coastal marine layers, and spring wind patterns that create unpredictable daily swings. This market specifically predicts whether San Francisco's high temperature will fall within the narrow 50-51°F band on May 2, 2026—a precise target accounting for only a one-degree range. The current 0% YES odds reveal strong market consensus that the actual high will fall outside this band, either significantly warmer or notably cooler. Such extreme specificity in temperature prediction is inherently difficult, even with modern meteorological forecasting. The San Francisco Bay Area's unique microclimate, influenced by cold ocean currents and marine layer formation, produces surprising daily temperature variations. A high of 50-51°F is technically plausible for May in San Francisco, but traders are confidently pricing this narrow outcome as highly unlikely. The market structure itself—isolating a single one-degree range among dozens of possible highs—explains the minimal trading activity and stark odds. Resolution uses the National Weather Service official daily maximum temperature recorded at the San Francisco downtown monitoring station.
Deep dive — what moves this market
San Francisco's climate during late April and early May represents a critical transition period between spring and early summer, characterized by increasing solar radiation competing against persistent marine influences. The Bay Area's unique geography—bounded by the Pacific Ocean to the west and sheltered valleys to the east—creates a complex thermal environment. The California Current delivers cold water along the coast year-round, while thermal heat absorbed by inland valleys creates powerful pressure gradients that drive the marine layer inland each morning. On typical May days, San Francisco experiences morning fog that often persists through late afternoon, suppressing afternoon temperatures. This pattern explains why the 50-51°F high is technically plausible for May 2, yet rare enough to attract minimal trader interest.
Factors pushing toward YES (50-51°F high): A persistent marine layer that fails to fully clear, combined with an unusually cool upper-level air mass, could restrict temperatures to the lower 50s. If high pressure remains offshore and a weak cold front lingers nearby, the marine layer stays entrenched and strong. Coastal upwelling intensification would lower sea-surface temperatures further, cooling air masses before they reach the city. A night of clear skies followed by marine layer re-formation could radiatively cool the surface and keep afternoon highs suppressed. Historical May data shows occasional days where the high reaches the low 50s, particularly in the first week before inland heat builds.
Factors pushing toward NO (outside 50-51°F): More likely scenarios have the high either well below 50°F (persistent fog, highs of 45-48°F) or well above 51°F (clear skies, strong inland heating, highs of 58-65°F). May weather in San Francisco is bifurcated: either cool fog-dominated days or warm inland-influenced days, with mid-range outcomes less common. The one-degree precision of the 50-51°F range is statistically poor—roughly 30 possible daily high outcomes exist across a 45-75°F range, making any single narrow band inherently low-probability.
The 0% odds correctly reflect the fundamental difficulty of forecasting daily temperatures with single-degree precision, even with modern weather models. Meteorological uncertainty naturally produces a range of plausible outcomes, not point predictions. Traders are making a statistical judgment: single-degree temperature ranges are sufficiently rare that they should never trade above near-zero odds.
What traders watch for
National Weather Service San Francisco forecast issued May 1: check predicted high temperature and timing of marine layer clearing.
Real-time temperature readings May 2 afternoon, particularly between 2-5 PM when daily highs are recorded in San Francisco.
Marine layer intensity and inland thermal heating—persistence of coastal fog suppresses temperatures; rapid clearing pushes highs above 52°F.
Upper-level air mass characteristics—cool trough proximity or warm ridge position will either suppress or elevate afternoon temperatures.
How does this market resolve?
The market resolves YES if the National Weather Service records San Francisco's official daily high temperature as 50-51°F on May 2, 2026. Resolution occurs after 11:59 PM on May 2 using the NWS downtown San Francisco monitoring station.
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.
