[PorterSq]

I'm not sure if this will do, but is your summer office a business suit workplace, or a jacket-and-tie workplace? In my thrifting experience, sack blazers aren't so tough to come by. It's the suits that are difficult to find (particularly those that don't require a ton of tailoring).

As a southerner, I suspect you know this feeling, but: It gets sticky in DC in the summer, so if you're going thrifting, remember to keep the fabrics light!

 

[PorterSq]

Solid advice from the guys above. One more thing to add (and I'm ready to take heat for this): it's OK not to dress 100% trad. There is some nice stuff available at Marshalls, Burlington Coat Factory, etc. that is cheap and will hold up nicely for at least the summer. Some even look "trad-like" in terms of colors and little padding on the shoulders. Those chains don't carry sacks as far as I know, but if you need a couple of suits on the cheap-cheap that look decent and hold up for the summer, you could do worse.