He was a Labor member of the New South Wales Legislative Assembly, representing Blacktown from 1962 to 1971 and Mount Druitt from 1971 to 1973.
He was educated at public schools in Mildura and Leeton and assisted his father on their farm.
He joined the Labor Party in 1929 and became active in the Australian Workers' Union.
In 1956 he became President of the New South Wales branch of the AWU, serving until 1961; he was also a member of the central executive (1957–1961).
Southee was buried beside his wife, Muriel at Pine Grove Memorial Park.