This is for the White House as it appears in the Simpsons. For an article on the real White House, see here.
The White House is the place where the President of the United States lives and works. When Bart had to study for a test he did not know the answers to on a snow day, he dreamt about the founding fathers meeting in the white house, the subject of the test. It suddenly starts snowing, disrupting Bart's dream and annoying him of the fact he can't go outside to play but must study.