I finally finished all of 2006 in terms of which sites had the coldest temps for each day. Here's a list of the days on which Mount Washington had the coldest temp anywhere in the USA (including Alaska and including ties):
Excluding Alaska, Mount Washington had the coldest temp in the lower 48 (including ties) on 51 days in 2006. I won't list all of those...
DATE MWO NEXTCOLDEST
2/19/2006 -28 -26(Olney, MT)
5/23/2006 19 23(Anaktuvuk Pass, AK; Bellemont, AZ; Fort Valley, AZ)
8/12/2006 31 31(Barrow, AK; Meacham, OR)
9/21/2006 23 25(Chicken, AK; Sunriver, OR)
10/6/2006 22 22(Northway, AK; Spincich Lake, MI)