WON climate

Will the minimum temperature be 48-49° on Apr 28, 2026?

The Setup

The market asks if SFO's minimum temperature today will fall into a narrow 2-degree window of 48-49F. While the historical average is near 51F, the crowd is monitoring whether a final pre-dawn dip will occur before the morning fog rolls in. This is a high-stakes technical weather play where real-time observations provide a significant edge over day-ahead forecasts.

With SFO sitting at 51F at 5:15 AM and 14 mph winds preventing a pre-dawn plunge, the 48-49F target requires a 2-degree drop that real-time conditions simply don't support.

Market

94c

Our Estimate

95-99c

Edge

+3c

Bull Case

Real-time observations show SFO at 51F at 5:15 AM PDT. With sunrise at 6:21 AM, there's only about an hour left for the temperature to drop the required 2-3 degrees. Typical pre-dawn cooling in this environment is only 1-2 degrees, which places the minimum safely above the target bin. Atmospheric conditions are actively inhibiting further cooling. SFO is reporting westerly winds of 9-14 mph and mostly cloudy skies with fog rolling in. Cloud cover acts as an insulating blanket, trapping terrestrial radiation, while the wind keeps the boundary layer mixed. Without clear skies and calm winds, the rapid radiational cooling necessary to reach the target bin won't occur. The synoptic setup favors a warming trend. The NWS Area Forecast Discussion explicitly calls for a slight warming trend for overnight lows, with the previous night's low at 52F. Major forecasting services like AccuWeather and the NWS official forecast converge on a low of 51F, keeping the minimum safely above the 48-49F range.

Bear Case

The current dew point at SFO is 46F, which provides a theoretical floor for the minimum temperature. If the cloud cover dissipates completely and the westerly winds decouple to calm conditions just before sunrise, radiational cooling could accelerate. This would allow the temperature to plunge into the 48-49F range without hitting the dew point floor. Historical variability at SFO occasionally produces late-season dips when high pressure to the north strengthens. In April 2026, SFO has already recorded minimum temperatures in the 48-49F range on two separate occasions. This demonstrates that the target range is a frequent occurrence when conditions are slightly cooler than average. The minimum temperature for the calendar day could theoretically occur just before midnight on Tuesday. If a cold front moves in or skies clear rapidly after sunset, the temperature at 11:59 PM on April 28 could hit 49F before continuing to drop into Wednesday morning.

What Could Go Wrong

IF the cloud cover breaks completely and winds drop to near-calm between 5:30 AM and 6:30 AM, THEN radiational cooling could accelerate, dropping the temperature the necessary 2 degrees to hit 49F. IF the NWS Climatological Report records a brief, localized temperature dip at the sensor that isn't reflected in the hourly METAR observations, THEN the official resolution could fall into the 48-49F range despite broader trends. IF a rapid clearing of skies occurs just before midnight on April 28, THEN the evening temperature could briefly touch 49F before the calendar day ends, triggering a YES resolution.

Get picks like this daily

Full analysis delivered to your inbox every morning at 7:00 a.m. ET.

Start Free Trial