San Francisco's climate in mid-April typically sees moderate temperatures as spring progresses steadily. April 20 marks the tail end of spring's early phase, when the city's daily high temperatures are usually influenced by broader Pacific weather patterns, including ocean currents and high-pressure systems that dominate coastal California. The prediction market for a high of 70-71°F reflects an exceptionally narrow, specific range—just one degree wide. Currently priced at 2% YES odds, this tight range is considered quite unlikely by traders, suggesting market consensus expects temperatures either noticeably lower, likely in the mid-60s, or meaningfully higher, potentially reaching the mid-70s or above. The market will resolve based on the official recorded high temperature for San Francisco on April 20, making the outcome objectively verifiable once the date passes and weather data is published. Weather prediction markets like this one show how prices shift continuously as meteorological forecasts update in the days and hours leading to resolution. The extreme rarity of this narrow 1-degree band makes it a precision test case—such extreme odds typically signal either insufficient market depth or overwhelming consensus that alternative temperature outcomes are far more probable.