Besides, we find dinosaur bones in Alaska and Atarctica.
"...Besides, we find dinosaur bones in Alaska and Atarctica...."
Additionally, remember that climate and weather patterns are not constant. During the Mesozoic, the earth's climate was generally quite a bit warmer than it is now. Go to this link:
http://www.scotese.com/climate.htm
and explore maps of the climate of the Triassic, Jurassic, and Cretaceous for a good overview.