What is the defining temperature characteristic used in climate classification systems (like Köppen) for the Polar climate zone (Group E), which prevents the growth of large trees?

💡 Explanation:

In major climate classification systems, the Polar climate zone (E) is fundamentally defined by the fact that the average temperature of the warmest month never exceeds 10°C (50°F). This threshold is critical because it marks the approximate boundary of the treeline; temperatures consistently above 10°C are generally required for the sustained growth of forest vegetation.