Nope. Dinosaurs were so big because the climate was hot and dinosaurs were ectotherms, meaning they would not bake themselves from the inside out since they do not generate their own body heat. Their large size allows them to keep the heat that their body has, since the larger an object, the less surface area to volume ratio becomes. That means a large object will gain and lose heat more slowly than a small one. In a cold climate, it would mean they would have a hard time warming up, but in a hot climate, they can conserve their body heat better without sunning themselves or sitting on a hard rock to absorb heat. .