• Extremely dangerous marine conditions across coastal California waters this week

    ByTeo Blašković

    Extremely dangerous marine conditions are developing across Northern and Central California waters this week, the National Weather Service (NWS) San Francisco Bay Area warned on Tuesday, December 23, 2025. Storm Force winds are forecast across the coastal waters with Gale Force winds extending into San Francisco and Monterey bays beginning Tuesday morning. Seas are expected to build to near 6 m (20 feet) under the strongest winds, posing life-threatening conditions for mariners.

  • Strong atmospheric river to bring heavy rain, snow, and flooding to California this week

    ByRishav Kothari

    A strong atmospheric river is forecast to impact California from December 23 to 27, 2025, bringing widespread heavy rainfall, flash flooding, and high-elevation snow. The system is expected to produce 250 to 500 mm (10–20 inches) of precipitation in parts of the Sierra Nevada and 150 to 300 mm (6–12 inches) in the Coast and Transverse Ranges. The National Weather Service has issued high-risk alerts for flash flooding across southern California and moderate winter storm impacts over the Sierra Nevada.

  • Strong atmospheric river to impact California, up to 500 mm (20 inches) of rain forecast for Sierra Nevada

    ByRishav Kothari

    Three atmospheric rivers are expected to impact California between December 20 and 25, 2025, producing 250–500 mm (10–20 inches) of rain over the Sierra Nevada and 75–180 mm (3–7 inches) over southern coastal ranges. The strongest system is forecast to peak on December 23–25 with IVT values surpassing 750 kg m⁻¹ s⁻¹ and AR3–AR4 intensity.

  • Above-normal atmospheric river activity forecast for Northern and Central California in late December

    ByRishav Kothari

    The Center for Western Weather and Water Extremes (CW3E) at UC San Diego forecasts above-normal precipitation for Northern and Central California between late December 2025 and early January 2026. The latest subseasonal outlook, issued on December 16, indicates high confidence in enhanced atmospheric river (AR) activity and persistent Pacific Ridge conditions during the period from December 22 to January 11, 2026.

  • Back-to-back atmospheric rivers forecast to impact the U.S. West Coast through December 20

    ByRishav Kothari

    Two atmospheric rivers are forecast to bring prolonged heavy rain and mountain snow to the Pacific Northwest and northern California through December 20, 2025. The Weather Prediction Center (WPC) forecasts 100–150 mm (4–6 inches) of precipitation across western Washington and 100–200 mm (4–8 inches) across western Oregon, with locally higher totals in the Cascades and coastal ranges.

  • Earthquake swarm in San Ramon continues with multiple events on December 15, California

    ByTeo Blašković

    An earthquake swarm that began near downtown San Ramon, California, in October remained active on December 15, with three earthquakes recorded within a few hours by the U.S. Geological Survey. The swarm is occurring in a structurally complex fault zone near the Calaveras Fault, where stress is released through repeated small ruptures rather than a single larger earthquake.