Just make sure you pay some extra attention to your coolant temperature. Your radiator is less efficient in the summer because the difference between ambient air temperature and your engine coolant temperature is smaller. On top of this, you're trying to displace more heat when the A/C is running. You really should take some temperature measurements because you're chipping away at the engineering tollerances of the cooling system; the extra capacity you need when climbing a hill or you have the ICE floored (I know we're not drag racers.) I'm being preachy because having a cracked or warped engine head from overheating sucks.

Another thing to consider is electrical losses from your radiator fan motor. At cruising speeds, passive air flow through the radiator is usually enough to keep things cool. However, with a restricted grill in the summer, I wouldn't be surprised if the electric fan is triggered more often. Just speculation, but worthy of investigation rather than assumption.