A/C Issues in '15 Forester

Hey, first time posting here, hoping to find some help.

I purchased my Forester used last October, and have so far loved every second of it. It's my first Subaru, and it's met nearly every expectation. I had no issues all winter long here in East Tennessee. Handled great, and the heater kept me nice and toasty all winter.

My issue has begun now that it's starting to heat up outside. When I first start driving, it pumps out nice, cold air. But if the temps get above 80, the A/C slowly starts going out, to the point that it will eventually start blowing out hot air. It's become completely miserable. My wife and I came home from Charlotte the other day, and had to make the whole trip with nothing but open windows. If it rains, it's enough to make me almost pass out from the heat. I can't take it anymore. I love this car, but it's getting to where I dread getting in it anymore. Note, as long as it's not over 80 or so out, the A/C will blow ice cold continuously. Also gets worse on interstate or after prolonged use.