Imagery and Tension in Storm Poetry

Read the following lines from a poem:

"As the storm clouds gather, dark and fierce,
The air crackles with electricity,

Nature's fury unleashed, the ground trembles,
Lightning quivers through the spine of the night.
Each thunderclap echoes like a war drum,

Beneath this darkened cloak, life pauses,
A breath held in anticipation..."

What imagery primarily enhances the sense of tension in these lines?