Which occurs first during a thunderstorm?

Lightning occurs first during a thunderstorm because it is actually the result of electrical discharges between charged areas within the storm cloud itself or between the cloud and the ground. The process that leads to lightning begins with the buildup of electrical charges due to the movement of ice particles and water droplets within the storm, resulting in a discharge that can produce lightning.

Once the lightning occurs, the rapid expansion of heated air causes thunder to be heard shortly thereafter. Rain typically starts to fall after the conditions within the storm have reached a point where water vapor can condense and precipitation begins. Wind often accompanies thunderstorms but does not precede them as a necessary element; instead, winds can be generated by the updraft and downdraft occurring during the storm. Therefore, lightning, being a product of the storm's electrical activity, is the first phenomenon to manifest.