Earthquake Weather? Scientists Debunk The Myth — What The San Ramon Swarm Actually Shows

After a recent swarm of small earthquakes near San Ramon, many Bay Area residents asked the familiar question: Is this earthquake weather? While the idea that calm, warm, or foggy conditions can trigger quakes is widespread, scientists say it has no basis in seismology.

Why The Myth Persists

The belief in "earthquake weather" dates back centuries. People naturally notice coincidences — an earthquake on a sunny day, or a series of tremors during a foggy morning — and infer a connection. In California, the weather patterns people associate with quake days are common, so overlap with seismic activity happens often by chance.

What Actually Causes Earthquakes

Earthquakes result from stress building and releasing along faults deep beneath the surface, often miles underground. Surface weather — rain, wind, temperature swings, or barometric-pressure changes — affects only the shallow crust and atmosphere and does not reach depths where tectonic stress accumulates. Large active faults such as the San Andreas and Calaveras are driven by tectonic plate motions, not short-term surface conditions.

The San Ramon Swarm

Seismologists link the recent San Ramon swarm to movement on smaller fault strands near the Calaveras Fault, part of the Bay Area's active fault system. Swarms — clusters of many small quakes over days or weeks — attract attention because people feel repeated shaking in a short period. Scientists emphasize that swarms are common in the region, are not caused by surface weather, and do not necessarily indicate a large quake is imminent.

What Weather Can Do (And What It Can’t)

• Heavy rainfall can increase groundwater or destabilize shallow soils and sometimes contribute to landslides or localized ground movement.
• There is no convincing evidence that storms or normal weather patterns trigger earthquakes on major tectonic faults.

Why Quakes Seem More Frequent

Two main factors explain the impression of increased seismicity: modern seismometers detect many more small quakes than instruments did decades ago, and apps, alerts, and social media make people far more aware of every shake. In reality, earthquakes have long been happening; we are simply better at detecting and sharing them.

Practical Advice

Instead of looking for a weather link, experts urge preparedness. Simple, effective steps include:

• Secure heavy furniture and appliances to walls.
• Learn and practice Drop, Cover, and Hold On.
• Keep an emergency kit stocked with water, food, meds, and important documents.
• Review family and workplace emergency plans regularly.

We can’t predict when or where earthquakes will strike, but preparation reduces risk and improves safety.

Original reporting by Roberta Gonzales of KTVU.