Which cloud type is white, puffy pillows with flat bottoms?

• A. Cumulus
• B. Cirrus
• C. Nimbus
• D. Stratus

Answer: (A)

Cumulus clouds are white, puffy clouds with flat bases. They form as warm air rises, cools, and condenses into rounded, cotton-ball shapes. The flat bottom comes from where the rising air stops at a stable layer, creating that distinct level base. These clouds usually signal fair weather when small, but they can grow taller into storm clouds if moisture and instability increase. Cirrus clouds are thin and wispy high in the sky, stratus clouds are flat, gray layers across the sky, and nimbus refers to rain-bearing clouds, often dark and widespread, not the bright, fluffy puffballs described here.