Newspapers will tell you when these showers will happen. When radio stations transmit, they send out electromagnetic signals in all directions. Many signals just keep on going right out into space if they don't meet an antenna. They reflect signals so that they bounce back to Earth. When these signals arrive, your radio picks up the stronger signal.
Meteors are visible every clear night of the year.
During meteor showers, up to one meteor appears every minute. The space dust that causes meteors is thought to be the remains of comets. As the Earth passes through this dust, gravity pulls some of the particles toward Earth at high speed. When they strike the atmosphere, friction causes the particles to vaporize and we see sudden streaks of light. Meteors showers are predictable, seasonal events.