Temperate broadleaf and mixed forests are a temperate and humid biome. The typical structure of these forests include four layers. The upper most layer is the canopy which is composed of tall mature trees. Below the canopy is the three-layered, shade tolerant understory. The top layer of the understory is the sub-canopy which is composed of smaller mature trees, saplings, and suppressed juveniles canopy layer trees awaiting an opening in the canopy. Below the sub-canopy is the shrub layer, composed of low growing woody plants. Typically the lowest growing (and most diverse) layer is the ground cover or herbaceous layer.
Temperate broadleaf and mixed forests occur in areas with distinct warm and cool season, which give it a moderate annual average temperature (5.5-15.6 Celsius). These forests occur in relatively warm and rainy climates, sometimes also with a distinct dry season. A dry season occurs in the winter in East Asia and in summer on the wet fringe of the Mediterranean climate zones. Other areas have a fairly even distribution of rainfall, annual rainfall is typically over 600 millimetres (24 inches) and often over 1500 millimetres (60 inches). Temperatures are typically moderate except in parts of Asia such as Ussuriland where temperate forests can occur despite extremely harsh conditions with very cold winters.