My commute is 7.5 miles each way, but hilly as f$%&. I don't wear my typical road biker clothes, but I do wear clothes that wick sweat. I also wear a backpack that consists of my laptop, a change of clothes, and snacks. I freshen up when I get to work. Of course you will have to discover what works for you; this is what works for me, so I encourage you to try it
Actually, I've settled on normal clothes, though making a few modifications.
I got a few pairs of stretchy old navy khakis with 2% spandex to wear while on the bike. Surprisingly very comfy, especially in cool weather, and they look like normal cotton pants. Those pants with a cycling jacket over a normal shirt, or thermal base layer under a normal shirt has been perfect since I started the new job in september. So, from ~75F to 15F I've been nice and comfy. I will say at the upper end of that range the decision was much more on the fence...I got a bit 'moist' with the khakis.
I work slightly weird hours, starting at 11am a few days a week. So, in the dead of summer, I may have to adjust things, either bringing in a change of clothes, or just riding very slow.
On the other hand...we are very casual here. Linen pants and a wicking polo shirt would be more than cool enough unless it's abominable out...like over 100 and humid.