San Francisco Hits Unexpected Warmth Amid Pineapple Express

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San Francisco saw surprisingly warm temperatures on Tuesday, with the city's official weather station hitting 68 degrees and some backyard stations recording 70 degrees. This unexpected warmth was due to a Pineapple Express, a moisture plume from Hawaii, that pushed temperatures well above previous forecasts and left the city in the 'warm sector' of the storm system rather than under thick clouds and drizzle.

Why it matters

The warm spell is an unusual weather event for San Francisco, which typically experiences cooler, cloudier conditions this time of year. The unexpected warmth highlights the unpredictable nature of Bay Area weather and the impact of larger weather patterns like the Pineapple Express on local conditions.

The details

Temperatures climbed well into the 60s across much of the Bay Area on Tuesday morning, with the potential to reach the low 70s in some areas. This warmth was driven by the Pineapple Express, a moisture plume originating near Hawaii, that pushed rain and clouds further north while leaving San Francisco under mostly sunny skies. Forecasters say the warm air pushed the rain-snow line above 10,000 feet, raising flood risk in the Sierra Nevada foothills and avalanche danger in the Tahoe backcountry.

• On Tuesday morning, San Francisco's official weather station at Mint Hill hit 68 degrees just before 11 a.m.
• Some backyard weather stations in neighborhoods like the Excelsior, Mission District, SoMa, Nob Hill and North Beach recorded 70-degree readings at the same time.

What they’re saying

What’s next

Temperatures are expected to remain warm through the rest of the week, with highs forecast to reach the mid- to upper 60s on Thursday and the upper 60s to low 70s on Friday. However, a cooldown is expected on Sunday as clouds and precipitation chances increase from a potential passing system.