A lightning bolt heats the narrow channel of air it travels through to tens of thousands of degrees, hotter than the surface of the sun, in a fraction of a second. That sudden, violent heating is the whole event: the flash is the superheated channel glowing, and the thunder is the shock of that air exploding outward. Monsoon thunderstorms are prime factories for it.
The charge builds inside the storm. In a tall convective cloud, colliding ice and soft hail strip and stack electric charge, light positive high up and heavy negative lower down, until the difference grows large enough to break down the air between cloud and ground and discharge in a stroke. A single towering monsoon cell can throw strike after strike for as long as it lasts.
Out here the danger has a particular shape, and it is the openness. The desert offers little shelter and few tall objects, so a person standing on a flat, high bajada is often the tallest thing around, which is to say the target. Getting low, off any rise, and inside a hard-topped vehicle or a building is not caution here; it is the difference that matters when a storm builds overhead.
There is a second hazard that does not need rain at all. In the monsoon a bolt can reach the ground from a storm whose rain evaporates before it lands, which is dry lightning, a strike with little or no wetting rain behind it. On dry brush that is a fire start with nothing to put it out, and it is a leading cause of natural wildfire across the Southwest. The storm can pass, leave the ground dry, and leave a fire behind.
You can measure a strike's distance by counting. Light arrives instantly and sound travels about a mile every five seconds, so counting the seconds between the flash and the thunder gives the distance; if you can hear thunder at all, you are already within range of the next strike.
When the count between flash and bang drops toward nothing, you are the tallest thing on a flat desert. Get down and get inside.