The Gravitron was a gravity-manipulating device that was installed on a base on the Moon around the 2050s in order to control the tides on Earth, so that they in turn could change the weather. It was very delicate: 5 units off-center and it could lift half of London into space. The powerpack powering the Graviton was thermonuclear with an inner temperature of 4 million degrees. It produces very intense sonic fields. Without protective helmets the operators inside the Gravitron room would be sent insane in as little as 12 hours.
In 2070 the Cybermen infiltrated the moonbase and tried to take control of the Gravitron, in order to use its gravitational effects to kill all life on Earth and thus eliminate it as a threat. However, they failed. (DW: The Moonbase)
The Gravitron did permit ordinary thunderstorms. (SJA: The Mad Woman in the Attic)