Here is my favorite outfit I found that that balances professional with "holy crap my face is literally melting off right now"
Note the patterned silk blouse that is perfect for walking to work in; there are a lot of silk tops out there this season with ruffles which I think is perfectly office appropriate if paired with the correct bottom- NOT Bebe mini skirt as mentioned in the previous post. A nice bold cardigan for the A/C vent your cubicle is inevitably under; and simple slacks, preferably machine washable because the sweat along the waistband- though not glamorous is going to happen.
If you're looking for more of a cool breeze on your way to work, a dress is a great option for summer and if you pick the right one you can transition it into winter with some warm tights and appropriate jewelry.
Here I've picked out an outfit that may fit that bill.
Dress, Jcrew, $98
love the ruffle around the neckline and the "orchid ginger" color will look good on you if you're pale or super-back-from-vacay-tan.
Belt, Talbots, $38
Feminine with studs add a bit of 'bitch, please, I'm wearing this dress'
Necklace, Ann Taylor, $46
Ann Taylor has really stepped it up in the accessories department. This one I would double wrap for extra volume.
Shoe, Payless, $7
Yes, you read that correctly. Never overlook the power of Payless. These little wedges are not only the perfect price but they can go from day dress to skinny jeans easily.