Altostratus is a broad midlevel cloud layer that can cover much of the sky, often making the Sun look like a dim disk behind frosted glass. It sometimes thickens ahead of widespread rain or snow.
What it looks like
Look for a mostly uniform gray or blue-gray veil with little distinct lumpiness. The Sun may shine weakly through thin sections, but ground shadows usually fade.
How it differs from cirrostratus
Cirrostratus is higher and thinner and can create ice-crystal halos. Altostratus is generally lower and more opaque, and the Sun’s outline appears blurred rather than surrounded by a distinct halo.
What happens next
With increasing moisture and lifting, altostratus can thicken into nimbostratus. That cloud type is more strongly associated with steady precipitation reaching the ground.
What it cannot tell you
A gray midlevel layer alone does not establish the exact timing or intensity of rain. Local fronts, radar and forecast data provide essential context.
Frequently asked question
Does altostratus always bring rain?
No. It may occur without significant precipitation reaching the surface.
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