The Himalayas extend over a vast longitudinal arc and are one of Earth’s most climatically diverse regions. This chapter explores the complex interplay between topography, elevation gradients, and global atmospheric systems—primarily the Indian Summer Monsoon (ISM) and Western Disturbances—that create this remarkable heterogeneity. From the humid, monsoon-drenched Eastern Himalayas to the arid western reaches, climatic conditions vary dramatically over short distances, profoundly influencing forest ecosystems across the range. The chapter examines altitudinal impacts on temperature through temperature lapse rates (TLRs), which vary seasonally, and from east to west along the Himalayan arc. It details precipitation patterns and their significant east-west and north-south gradients, explaining how orographic effects create rain shadows and localised microclimate variations. Special attention is given to mountain-valley wind systems that influence local temperatures, fog prevalence, and moisture distribution. Climate change impacts on the Himalayas are addressed, noting that while the region is warming faster than surrounding areas, precipitation trends remain variable and inconclusive. The chapter discusses the unprecedented changes in the Himalayan cryosphere, including accelerated glacier melt and the implications for river discharge and water availability. The differential vulnerability of major river basins, viz. Indus, Ganga, and Brahmaputra, to climate change is analysed based on their varying dependence on snowmelt contribution. This exploration of Himalayan climate provides the foundation for understanding how forests in the region respond to both natural climatic variability and the accelerating pressures of global climate change, setting the stage for subsequent chapters on forest associations and ecosystem responses.