The theme to The Addams Family One of the most popular sound effects is thunder. Add a bright flash of light and you have thunder and lightning. The trick is to synchronize the sound of the thunder and the flash of lightning. A light organ is a piece of equipment, often used by disc jockeys at parties, to flash colored lights with the beat of the music. After adjusting the sensitivity, when the thunder booms, the lights will flash.
Some people like to use strobe lights for the lightning.
I have been told that flood lights work better. Strobe lights tend to be fickle, requiring all sorts of electronics to get them to flash intermittently. Flood lights are generally cheaper and easier to work with. You can buy the floodlight sockets with an attached stake for outdoor use. Simply stake them in your yard.