The seven Smithsonian Museums located on the Mall will be open on Inaugural day. Great places to warm up. The Castle (administrative offices near the Merry-Go-Round) is the best place to hit the bathrooms.

http://www.gosmithsonian.com/inauguration


There are unsightly porta-potties all over the place. And there have been porta-potties on the Mall for the past year, near the National Gallery of Art and Natural History Museum.

I live on Capitol Hill and have been layering up just to walk my dog. Single-digit temps Thursday and Friday nights. Last I checked, tomorrow night's low will be 19 degrees. So I'd be planning for temps in the 20s. Here's what I'd be wearing on Tuesday (in fact I will be walking my dog around the Capitol):

Parka w/hood + lots of pockets
Fleece hat-neck gaiter-ear warmers, 1/2 face mask (which also warms the neck and can be rolled down to not look alarming to security)
Ski gloves
Smartwool ski socks
boots
long underwear
smartwool top + fleece-lined 1/4 zip

chemical hand warmers

Kleenex mini-packets (useful for tp)

The crowds will probably be smaller than forecast in part because of all the hysterical press reports on mass crowds.