Which climate has a mean temperature below 10°C during the warmest month?

The correct answer is Polar climates.

The polar climate areas are featured by an absence of warm summers. Each month in a polar climate exhibit a mean temperature of fewer than 10 degrees Celcius. Even in their warmest months, they have a mean temperature of fewer than 10 degrees Celcius.

The countries coming under the polar climate regions are Alaska (United States), Yukon (Canada), Greenland (Denmark), Finland, Norway, Iceland, Sweden, and Russia.