Why a Cloud Sitting on Top of a Fire Cloud Means Something

Wildland fires sometimes build towering, smoke-infused clouds of their own. In summer 2026 scientists flew out to intercept and study them, and during an August 11 flight over the Sand Creek fire in Montana they came back with a bonus: observations of an ephemeral pileus cloud hovering atop one of those towering fire clouds. Pileus clouds are smooth and veil-like, well known to atmospheric scientists and cloud lovers, and regarded as signs of especially vigorous convection. Seen above a fire cloud, the little cap is less a separate weather feature than a marker of how hard the updraft underneath is pushing.