Many photographers say that light is the most important factor when it comes to taking pictures of landscapes.
I don't think that's quite right.
Clouds have the biggest impact. Technically speaking, sunlight is constant and never changes. Light is always visible, but the clouds determine how much light escapes to the earth below. Clouds diffuse the light to create magic. They reveal light to create amazing scenarios. Clouds themselves absorb light and become even more important subjects than the land below them. Their shapes create drama and mood. Often times, the story is lost without them.
You better be sure that when there are strange cloud conditions forming, I'm most likely running around with my camera or staring obsessively at it waiting for the moment I can.