There's an urban legend that extended hot weather causes earthquakes, because the heat causes the earth to crack.

An earthquake is the sudden release of energy within the Earth. This energy travels outward from a central point in the form of waves that cause the ground to shake. While other processes can and do generate quakes, the vast majority are caused by sudden movement along cracks in the crust that we call faults. They are not, as another person suggested, caused by particularly hot weather. -------------- Jimmyp wrote, "But some people talk about earthquake weather. I wanted to know what they are referring to." I am sorry, I misread the question. However, I don't believe in earthquake weather. One thing that you need to understand is that it takes time for heat to penetrate from the surface into the ground. Because of this, the deeper you go into the Earth the less variation there is in temperature over time. By the time you get to something like thirty feet below the surface, the temperature becomes constant at the average annual temperature for the region. The movement that causes earthquakes usually starts at depths that many times greater than this. So, the short term temperature variations associated with "earthquake weather" is really extremely unlikely to trigger an earthquake.

As someone who lived in San Francisco for a long time, Earthquake Weather is an unpleasant hot spell - enough to make people feel edgy and feel a kind of foreboding Weather, however, doesn't cause earthquakes.