Will San Francisco's high reach 50-51°F on May 19? Current odds: 1%. This prediction market reflects the narrow range's rarity during late May.
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San Francisco's geographic and climate characteristics during May typically produce high temperatures in the 55-65°F range, influenced by the city's distinctive maritime climate and coastal marine layer effects. The 50-51°F constraint is exceptionally narrow and unusually cool for late May, making this outcome statistically unlikely. At 1% current odds, traders are pricing in the rarity of a precise, sub-55°F maximum temperature during a month that rarely sees such cool conditions even at the coldest part of the morning. The Bay Area would require a significant weather anomaly—an unexpected cold front, persistent marine layer, or unseasonable arctic air—to reach this narrow band. NOAA daily high temperature readings from San Francisco International Airport or the National Weather Service serve as the authoritative resolution source. The market reflects trader conviction that warm-season May weather patterns will dominate, with only a small probability of the atmospheric conditions needed to keep highs in the 50-51°F range throughout the entire day.
San Francisco's geographic position and coastal climate create one of the most temperate weather patterns in North America, with relatively stable conditions year-round. May marks the transition into the warmer season, when solar angle increases and daytime heating becomes more pronounced. Historical temperature records from the San Francisco National Weather Service office show that May highs typically range from 55-65°F, with the average high around 63-65°F. Temperatures in the 50-51°F range are exceptionally rare during this month and would require sustained suppression of normal late-spring warming. The marine layer—a cool, moisture-laden air mass that forms over the Pacific—plays a crucial role in San Francisco's climate. While the marine layer often keeps mornings cool and can suppress afternoon heating even in summer, it typically breaks up by late May as the season advances. For temperatures to remain stuck in the 50-51°F range throughout May 19, the marine layer would need to persist unusually strong, or a cold front would need to move into Northern California. Cold fronts during May are possible but relatively uncommon after the spring storm season peaks in April. The current 1% odds reflect trader assessment that such conditions are highly improbable. Factors pushing toward YES include an unusually strong marine influence, an unexpected late-spring cold front, or a rare high-altitude trough bringing cooler-than-normal conditions to the California coast. Recent La Niña phases have sometimes correlated with cooler-than-average conditions in parts of the West, though their predictive power for a specific 50-51°F range on one day remains limited. A major upper-level low-pressure system could theoretically suppress temperatures, but such setups are increasingly rare as May progresses. Conversely, normal late-May patterns strongly favor NO. May climatology overwhelmingly supports warmer highs—typically 60°F or above. Even cloudy or overcast days in San Francisco rarely produce highs below 55°F by mid-May, and the narrow 50-51°F band is simply inconsistent with seasonal heating trends. El Niño patterns, when present, tend to support slightly warmer-than-normal conditions on the West Coast. The broad atmospheric pattern across the Pacific during mid-May 2026 would need to be dramatically different from typical May conditions to push temperatures into the 50-51°F range. The 1% probability encoded in current odds suggests near-certainty among traders that normal May weather will prevail, with only a slim acknowledgment of tail-risk cold-front scenarios. This reflects a rational assessment of climatology and the statistical rarity of such a specific, cool outcome during a month when San Francisco's maritime climate typically moderates toward seasonal warmth.
Market resolves YES if San Francisco's official high temperature on May 19, 2026 falls between 50-51°F according to NOAA data. Any reading outside this narrow range resolves as NO.
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