While the polar ice caps are colder in terms of average temperature, the tundra is considered a biome because it supports a unique ecosystem with distinct plant and animal life.

Here's why the tundra is considered the coldest biome:

* Low Temperatures: The tundra experiences extremely cold temperatures year-round, with average temperatures below freezing for most of the year.

* Permafrost: The ground is permanently frozen, which limits plant growth and creates a challenging environment for animals.

* Short Growing Season: The growing season is very short, typically lasting only a few months during the summer.

Let me know if you'd like to learn more about the tundra biome!