Answer:
Cold winter.
Step-by-step explanation:
The first Americans that migrate to North America did it at the height of the last ice age.
For survival in the journey, most of these people relied on foraging hunted animals. They did not have a profound knowledge in agriculture, so there were no food sources from crops such as wheat or potatoes.
They catch various animals that they passed through within the migration (such as deers). They utilize the meat for food, the skin to create the coats that kept them warm. In some extreme cases, they even need to put themselves inside the animals body and use it as shelter to protect them from extreme cold.