Which is a visual indicator of unstable conditions?

• A. Clouds grow vertically
• B. Stratus type clouds
• C. Poor visibility
• D. Steady winds

Answer: (A)

Unstable atmospheric conditions show strong vertical motion, so the visual cue is clouds that grow upward into towering cumulus or even cumulonimbus. This vertical development means buoyant air is rising freely, signaling convection and enhanced mixing, which in wildfire terms can drive more intense and erratic fire behavior.

Stratus-type clouds sit in stable air and stay flat, with little vertical growth, so they don’t indicate instability. Poor visibility can result from smoke, dust, or fog and isn’t a reliable sign of atmospheric instability by itself. Steady winds describe a wind-speed condition rather than the presence of vertical motion in the air, so they don’t signal instability either.

So, seeing clouds grow vertically is the clear visual indicator of unstable conditions.