Need help -- No island of the sea could be exempt

"As the men trooped heavily back into the front room, the two little windows presented views of a turmoiling sea of snow. The huge arms of the wind were making attempts- mighty, circular, futile- to embrace the flakes as they sped. A gate-post like a still man with a blanched face stood aghast amid this profligate fury. In a hearty voice Scully announced the presence of a blizzard. The guests of the blue hotel, lighting their pipes, assented with grunts of lazy masculine contentment. No island of the sea could be exempt in the degree of this little room with its humming stove. Johnnie, son of Scully, in a tone which defined his opinion of his ability as a card-player, challenged the old farmer of both gray and sandy whiskers to a game of High-Five." ("The Blue Hotel" by Stephen Crane) http://www.4literature.net/Stephen_Crane/Blue_Hotel/

Please help me to get what Crane means bu the blue sentence.

Thank you.

Cadzao.