Since the desert air was so dry, the bread quickly turned stale. In this sentence, the word SINCE serves as a clue that there is cause and effect.

I was in the National Forest with my camera. The day was crisp, and the leaves were turning gold and red. When I spotted the white-tailed buck, I froze. He wasn't more than 15 yards from where I was standing. The wind must have been right, because he kept on browsing the mossy ground. I lifted my camera very slowly. Carefully, holding my breath, I lifted the camera to my eye. Turning the focus ring, I framed the deer's head. Just as I was ready to press the shutter release, the buck raised his head. He was looking my way with wide eyes. Click. I took the picture. An instant later, the deer bounded away into the forest. He took off, but I had the shot. Today, the framed photo of that buck hangs above our fireplace. The deer was not able to pick up his scent is what the author is implying in the phrase "the wind must have been right".