These are some basic assumptions I have made when writing the story. I will update this post as needed.
· The horse collar was already invented.
· Certain plants and animals have adapted to the harsh conditions of Planetos and are not necessarily the same as their Earth equivalents. This might result in different behaviors or habits. I will specify these differences in the story if need be, and I might give greater detail in the Additional Information section.
· That there are many rivers on Planetos that are not on major maps, just like on Earth.
· Seasons: The seasons on Planetos are varied and longer than Earth. Though the seasons are typically the same length, Winter and Summer will always be longer and each can vary wildly. So you might have 4 months of spring, 2 years of summer, 4 months of fall, followed by 2 years of winter. Just like on Earth, temperatures vary throughout the year somewhat, like one day in Winter might drop 10 degrees, then rise back up. Or maybe a week of warmer weather. However, winter and summer time lengths might fluctuate. Winter might be longer in one cycle, summer the next. The difference might be small or large, but in the grand scheme of things (talking on the scale of planetary history) they equal out. The Neck acts as a major barrier for the weather. Above the neck winters are much more severe than below (at least on Westeros). Below the Neck, the farther south you go the warmer it gets. The Reach can produce reduced amounts of food in mild winters, and none in the coldest.