Wish I could say I have an 'average' but it depends on the lawn and the pool ...
Last November, we had to replace the liner in my inground pool. That was approx ~25,000 gallons.
I then had to partially drain and refill this September before I closed it because of a wrinkle. Figure another ~15,000 gallons for that.
We also had a pretty hot summer so I had the sprinklers cranked up. Trying to rejuvenate the lawn so it needed quite a bit of water.
We're on the high side of usage for a 3-person family, but we also have company pretty much every day (my wife's a teacher) all summer.