Changing water level

I have a pool of water using the daytime water prefab. I'm trying to make a script that slowly changes the water level depending on the weather and am stumped as to how to do this. So far I've got

 function Update() {
     if(weather == "partly cloudy") {
         if(transform.position.y != 33.00) {
         }
     }
     if(weather == "cloudy") {
         if(transform.position.y != 35.00) {
         }
     }
     if(weather == "raining") {
         if(transform.position.y != 37.00) {
         }
     }
     if(weather == "sunny") {
         if(transform.position.y != 31.00) {
         }
     }
 }

But from there, I have no clue how to actually make it go to the preferred position. Any help would be greatly appreciated.