You may want to try a corporate apartment. These are fully furnished units that are made available on a short-term basis for renters, just like you, who only plan to be in the area temporarily.
Most corporate apartments do not require the renter to sign a standard, 12-month lease. Rather, they can be leased for six months, three months or even one month.
To find a suitable apartment, check the Advanced Search page and configure your search to reveal only the properties that offer corporate leases.
First, enter your desired neighborhood in the Location field – you can even search all of Washington, D.C. if you like. Then, make sure to check the “Corporate” box under Other Housing Types Offered, and you’re all set.
See the link below for an example. I ran a quick search for corporate apartments in Northwest, D.C. Of the more than 300 units in Northwest, 16 came back as an exact match for corporate apartments.
http://www.apartmentshowcase.com/search/district-of-columbia/northwest/a-10
Best of luck to you!