2003 Subaru Legacy CAR TEMP HIGHER WHEN AC IS ON

I have been noticing my temperature gauge is running higher then normal with the AC on. Mainly on the highway not around town. Also only when the outside temps are higher. On my way to work in the morning usually 75º outside it's fine. When I go home in the evening it runs hot, it's about 90º outside. About 3/4 to red on temp gauge. Replaced the thermostat already.