Based on climate:
* Temperate country: This is a common choice, as it refers to countries with moderate climates, unlike the hot and humid tropical climate.
* Arctic country: This specifically refers to countries located in the Arctic region, which are known for their cold and icy conditions.
* Polar country: This is a broader term encompassing countries in both the Arctic and Antarctic regions.
* Arid country: This refers to countries with very dry climates, often found in deserts.
Based on geography:
* Continental country: This refers to countries located on continents, as opposed to tropical islands.
* High altitude country: This refers to countries with significant mountainous terrain, often with colder climates than tropical regions.
Based on cultural association:
* Developed country: This might be used if you're thinking about the typical associations with tropical countries as being underdeveloped or less advanced.
Ultimately, the best antonym depends on the specific context and what aspect of "tropical country" you want to contrast.