Why do we see more mirages in southern states and in the summer than at other times or places

Mirages of the desert type (what looks like water on a hot surface) require ground temperatures much hotter than the air above. The reduced air density near the ground causes light waves to bend upward, creating the mirage effect. This is most likely to happen in summer months, and where the sun is high overhead. There can also be strong mirages at Arctic locations however. Read about the "Novaya Zemlya effect" off the arctic coast of Siberia.