Where you do squats does not matter at all. What matters is how anatomically correctly your squats are performed. Practice them outside or inside – the effect will be wonderful anyways. You will tone up your whole body and strengthen your muscles. You can load a backpack with a couple of heavy items (a bottle of water, books, etc.) to make the exercise more challenging. There are a lot of variants of this activity. Try them all out and work out every morning.