The winger left Valencia for City last summer.
Silva told City's website: "I remember getting the news City were interested in signing me during my last matches with Valencia.
"I wanted to keep a clear mind after the season with the World Cup approaching and I decided I was ready for a fresh challenge. I had heard a lot of good things about Manchester and it was clear that City's ambition matched my own.
"I know that the weather in Manchester is different than Valencia or Canaries, but I come to Manchester to play football in a great team, not for sunbathing or going to the beach!"