SF May 19 High at 54-55°F: Market Says Almost No Chance

San Francisco’s weather on May 19 is already being called, at least by the traders holding this contract. A 1.8% implied probability on YES means the market has concluded that the city’s high temperature landing in the 54-to-55-degree Fahrenheit window is almost certainly not happening. That’s not a close call. That’s a market that has moved on.

The contract asks a specific question: will the highest recorded temperature in San Francisco on May 19, 2026 fall within the 54-55°F band? The YES price sits at 0.02. The NO price sits at 0.98. With resolution set for 2026-05-19 12:00:00, traders have less than 48 hours to see if the data proves them wrong.

How the San Francisco Temperature Contract Works

This contract resolves YES if San Francisco’s peak temperature on May 19, 2026 falls between 54°F and 55°F, inclusive. It resolves NO if the high lands anywhere outside that two-degree window. The resolution source is the market itself, drawing on official temperature records for the city. A YES outcome requires the thermometer to hit a very specific, narrow range on a single calendar day.

• YES (54-55°F high on May 19): Price 0.02, implied probability 1.8%.
• NO (any other high temperature): Price 0.98, implied probability 98.3%.

The NO side pays out under almost any weather scenario. San Francisco’s average May high sits closer to 62-65°F for mid-month. A 54-55°F reading would require an unusually cold air mass to stall over the Bay Area. That’s not impossible, but the city’s coastal climate in late May trends warmer than this window. The market reflects that gap.

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Momentum and Market Signals

The momentum composite here is flat: a 1-hour change of +0.0%, a 24-hour change marked N/A, and a trend score of 50.88. Combined, that signals a market in stasis. No new weather data or forecast shift has moved this price. The contract has settled and traders are waiting for the clock to run out.

Total volume on this market is $5,905. The 24-hour figure of $48,191 is actually larger than the total, which reflects how the data fields are structured here rather than actual trading activity. Liquidity sits at $5,554. This is a thin market. Low liquidity means a single meaningful trade could move the YES price sharply, even this close to resolution. That’s worth watching, but it doesn’t change the underlying weather math.

• The 1-hour price change of +0.0% combined with a flat trend score of 50.88 confirms no catalyst moved this market in the last session.
• Total market volume of $5,905 is well below the threshold where institutional conviction becomes readable. Thin liquidity means price signals carry limited weight.
• The YES price of 0.02 reflects a two-degree temperature window in a city where May highs rarely dip that low. The market is not pricing science incorrectly here.
• No large recent trades are recorded. Trader sentiment registers as strongly bearish, with 98.3% of contract value sitting on NO.

Lines Analysis: San Francisco Temperature on May 19

The case for NO rests on basic climatology. San Francisco’s coastal microclimate moderates temperature swings, but May is not a cold month in the city. The average daily high in mid-to-late May typically ranges from the low to mid-60s Fahrenheit. For the thermometer to peak in the 54-55°F band, a cold marine layer would need to dominate the day completely, suppressing the afternoon high by 8 to 10 degrees below seasonal norms. That kind of pattern exists, but it’s not what current late-May conditions typically produce.

What keeps the YES side from being at zero is the unpredictability of San Francisco’s fog dynamics. The city is famous for temperature inversions and cold June-gloom patterns that sometimes arrive early. A strong marine push could theoretically suppress the May 19 high into the 54-55°F range. Here’s what the measurements are telling us: that scenario is real but rare, and the market has priced it at roughly one-in-55 odds.

Signals to monitor before 2026-05-19 12:00:00:

• National Weather Service San Francisco Bay Area forecasts issued for May 19 are the single most important data point. Any forecast showing a high in the upper 50s would move the YES price.
• NOAA marine layer tracking for the Northern California coast directly affects whether coastal fog suppresses afternoon temperatures enough to matter.
• Surface pressure readings over the Pacific will indicate whether a cold, high-pressure marine system is pushing onshore in the 24 hours before resolution.
• Temperature readings from San Francisco International Airport and downtown stations in the early morning hours of May 19 will signal what the afternoon trajectory looks like.

At a YES price of 0.02, the market is clear about where it stands. The data favors NO by a wide margin. The only event that would reprice this contract before the 2026-05-19 12:00:00 resolution is a National Weather Service forecast showing the May 19 high dropping into the 54-55°F window, which would require an unusually strong cold marine event with less than 48 hours of lead time.

LINES VERDICT

Market Has Settled on NO

San Francisco’s May climatology does not favor a 54-55°F daily high, and the market has priced that gap correctly. The data doesn’t care about the politics, and in this case, the data and the market are saying the same thing.

What the market says: A 1.8% implied probability translates to roughly one-in-55 odds on YES. The market is pricing uncertainty, not science, and in this narrow temperature window with this short a time horizon, almost no uncertainty remains. Any volatility between now and 2026-05-19 12:00:00 would require a dramatic last-minute weather shift.

Key unknown: The National Weather Service’s May 19 forecast for San Francisco is the only data release that matters now. A cold marine push showing up in the 48-hour model run would be the single event that could force YES traders back into this contract.

Scientific Context

San Francisco sits at the edge of a coastal climate zone where marine layer dynamics, not continental air masses, drive daily temperature outcomes. The city’s May high temperatures have historically ranged between 58°F and 68°F for mid-month dates, based on multi-decade NOAA station records. A reading of 54-55°F would fall more than one standard deviation below the seasonal mean for late May. Cold days at this level do appear in the historical record, but they cluster more commonly in June and July, when the marine layer intensifies. The 1.8% probability on YES aligns reasonably well with the historical frequency of such cold days in this specific part of the month. Before 2026-05-19 12:00:00, only a confirmed forecast shift would change that picture.

Frequently Asked Questions

• What does a 1.8% probability mean here? It means traders collectively assign roughly one-in-55 odds that San Francisco’s May 19 high lands in the 54-55°F range. It is not zero, but it is very low.
• What does the NO contract pay out on? The NO contract resolves YES if San Francisco’s high temperature on May 19, 2026 falls anywhere outside the 54-to-55-degree window, which includes both warmer and colder outcomes.
• What data event would move this price? A National Weather Service forecast showing the May 19 high dropping into the upper 50s Fahrenheit would be the clearest signal to watch. Any confirmed cold marine layer forecast would pressure the YES price upward.
• When does this contract resolve? Resolution is set for 2026-05-19 12:00:00. That is less than 48 hours from the current timestamp of 2026-05-17 22:12:58.
• Is this market liquid enough to trust the price? Total market volume is $5,905, which is thin. Low liquidity means a single large trade could move the YES price sharply before resolution. Treat the price as a directional signal, not a precise probability.

This analysis reflects market conditions as of 2026-05-17 22:12:58. 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.