According to major climate classification systems used in geography, what specific temperature criterion must the warmest month of the year meet for a region to be designated as having a Polar climate zone (Group E)?

💡 Explanation:

The Polar (Group E) climate zone is fundamentally defined by its lack of a true summer. The key boundary used in systems like Köppen is the 10°C (50°F) isotherm for the warmest month. If all months of the year average below this temperature, the climate is classified as Polar (E).