There are 3 main places lightening can travel from. The ground to a cloud, a cloud to a cloud, and the cloud to the ground.
Scatter-plot shows correlation between two different variables (one on the y-axis, the other on x-axis). If there is linear correlation, the scatter-points form a straight line from zero (origo) to some direction. The more cloud-like distribution the scatter-plot does have, the less those variables in question have correlation or dependence with each other.
It depends on a size of a cloud.
Cloud or clouds is mentioned 17 times.
Yes, the noun 'cloud' is a countable noun; the plural form is clouds.