The Mesozoic era, which began about 240 million years ago and ended about 65 million year ago, is commonly referred to as the "Age of Reptiles." During that span of time the Earth evolved from one continent to many continents, as the land masses migrated to more or less the positions on our Earth that we see today.
So too, as time progressed so did the evolution of all living things that were alive during the Mesozoic era of time. The Earth's climate, slowly but surely, also changed to a cooler environment, in regard to the migration of some of those land masses that moved farther to the South or farther to the North.
In it also believed that the early dinosaurs were mostly cold-blooded creatures. In other words, their body temperature was equal to the temperature of their environment. Those dinosaurs were less active in cold weather. That is also true today for those creatures that we know as reptiles, which are also cold-blooded. Recent information came to light about the possibility that some types of dinosaurs were warm-blooded animals, but it is quite clear that those types of dinosaurs were few in number.
Then, like now, most reptiles, including dinosaurs, lived within a sub-tropical or tropical climate. There too is where most of the prehistoric plant life is found. Because of the location of the single continent known as Pangaea, it is quite clear that the environment was most favorable for the early evolution of life on our Earth. The greenhouse effect also contributed to the average warmer temperature that existed those many millions of years ago.
It is also true that animals of any kind usually live near the food in which they consume. Those early dinosaurs usually ate each other, as well as the plants, insects and the other things that were available. Like the reptiles of today, most of those dinosaurs were meat eaters. As time passed, some of those creatures evolved into the plant eating variety of dinosaurs. Then again, in freezing temperatures there usually is, if any, very little green vegetation available to eat. Then agin, some dinosaurs lived in the seas during those prehistoric times and therefore it is safe to believe that they too lived within the warmer waters of our Earth. So too, those warm-blooded dinosaurs would have to live in an area where food was available. That means that they would probably live among those cold-blooded dinosaurs.
Therefore, it safe to believe that most dinosaurs did live in a tropical or a sub-tropical climate until the creation and the movements of the continents resulted in weather conditions that many dinosaurs were unable to survive within. Then again, how many reptiles live within the North Pole or the South Pole?