Runner Game Background Softly Change

Hi guys, I'm making a runner game like Jetpack Joyride. I made a script to move my background using a second camera + a "Quad". Well, what I don't have any ideas of how to do is changing the background softly once my script just set a new texture to the Quad. Ex.: There is a texture running, a few seconds later, BOOM, other texture is there. My script for changing the background is something like this

@edit: full script here:

 public class ScrollScript : MonoBehaviour {
 
     public float speed = 0;
     public Renderer rend;
     public Texture[] Cenario;
     private float tempo;
     private int i = 0;
 
     void Start() {
         rend = GetComponent<Renderer>();
         tempo = 0;
 
     }
     
     // Update is called once per frame
     void Update () {
 
         tempo += Time.deltaTime;
         rend.material.mainTextureOffset = new Vector2 (Time.time * speed, 0);
 
     while (i <= 7 && tempo >= 2) {
             rend.material.mainTexture = Cenario[i];
             i++;
             tempo = 0;
             if (i == 7) i = 0;
         }
 
 
     }
 
 }