云隙光是从云雾的边缘射出的阳光，照亮空气中的灰尘而使光芒清晰可见。

对地面的观测者而言，只要有云或雾遮挡住太阳，就有可能看到此现象，但最重要的还是水气与灰尘的条件。因此云隙光在多云的天气比较常见；晴朗的日子里，则常发生于日落。比较好的观测地点在海滨或湿气重的山谷地区。

其物理原理则是粒子分散在空气中，形成胶体，被光照射后产生丁达尔效应。

偶尔云隙光会伴随着反云隙光一起发生。

Crepuscular rays /krᵻˈpʌskjᵿlər/ (also known as sunbeams, Sun rays or God rays), in atmospheric optics, are rays of sunlight that appear to radiate from the point in the sky where the sun is located. These rays, which stream through gaps in clouds (particularly stratocumulus) or between other objects, are columns of sunlit air separated by darker cloud-shadowed regions. Despite seeming to converge at a point, the rays are in fact near-parallel shafts of sunlight, and their apparent convergence is a perspective effect (similar, for example, to the way that parallel railway lines seem to converge at a point in the distance).