Montana was pretty far north during the Late Cretaceous. But the continents were much smaller and thus the climate was less continental and more temperate.
Actually some of those paleontological findings are not as much world climate, but location.
Montana wasn’t at the latitude and longitude it is now. There have been major shifts in tectonic plates. There was Gondwana and Pangea when conitinejts were all together.
Montana was pretty far north during the Late Cretaceous. But the continents were much smaller and thus the climate was less continental and more temperate.