A late May storm brought heavy rain to the Bay Area and snow to the Sierra Nevada on May 28, 2026 [1].
The event is significant because it delivered an unusual volume of late-season precipitation to the U.S. West Coast, extending the viability of mountain ski slopes into the spring.
Meteorologists said the unusual weather was due to an Omega block pattern [3]. This specific atmospheric configuration trapped the storm system over the region, leading to intense localized rainfall and high-altitude snowfall [3].
The impact on the Bay Area was severe. San Francisco received nearly a month’s worth of rain in a single morning [1]. In Davis, California, the storm delivered nearly a month’s worth of rain in one day [2].
While urban areas dealt with flooding, the Sierra Nevada mountains saw a surge of snow. This late-season accumulation was sufficient to keep at least one ski slope open for skiing [1].
Across the broader West Coast, millions of people are bracing for the effects of these weather conditions [3]. The storm's intensity stands in contrast to typical late-May patterns, where precipitation generally declines as the region enters the dry summer season.
“San Francisco received nearly a month’s worth of rain in a single morning”
The occurrence of an Omega block in late May demonstrates how stagnant high-pressure systems can disrupt seasonal norms. By forcing moisture-rich storms to linger over Northern California, this pattern creates volatile shifts in water availability and temperature, potentially impacting wildfire risk and water management strategies for the upcoming summer.
