Thunderstorm

A thunderstorm is a weather condition which takes place randomly during some rain- or snowfalls. All changes from these weathers apply, but since lightning occurs and the light level falls below 7, thunderstorms are distinct. Even in the middle of the daytime, hostile mobs will be able to spawn. However, far fewer mobs will spawn relative to night since it is just barely dark enough for them to spawn.

Lightning is a lethal element to the storm. It strikes randomly across the map, creating brief fires. While most are put out almost immediately by the rain, it will once in awhile ignite wood and other flammable blocks successfully. Lightning striking uses the same sound as TNT or a Creeper exploding.

You can also build a Lightning conductor, pictured below. This will prevent lightning striking anything else within the radius (How large the radius is, is unknown)



Trivia

 * If lightning manages to strike a portal frame, it will activate the portal.
 * Strangely, you can sleep in a bed during a lightning storm, regardless if it is daytime or nighttime.