AC usualy blows hot but not always

My Saturn Vue AC blows hot - usually.
When the air temp is cool, as when it's raining, it blows cold like it should (moving or idle)

Had a mechanic look at it. Says the freon pressure is fine and the clutch is engaged when it's blowing cold as it should be. Also not a fuse problem.

This is twice now, a couple of weeks apart, when it's been cool when it was cool out, the rest of the time it's blowing hot.