Minecraft wiki entry for Thunderstorm, associated text: As with rain and snow, the sky is darkened and the sun, moon, and stars are no longer visible. Thunderstorms darken the world, causing the light level from the sky to visually decrease to 10. The clouds darken from white to dark gray, although clouds themselves do not precipitate or create lightning. While the sun is not visible during rain, the glow associated with sunrise and sunset is still visible.