Terrain: The main physical feature is north-west to south-east oriented Shivalik Ridge, which runs through the middle of the national park. Motichur and Rajaji lie to the north and south of this ridge, respectively. Rajaji and Motichur are dissected by ravines which descend gently from the main ridge, becoming broad and full of boulders and pebbles. Streams remain dry for most of the year except in the monsoon, when they become rushing torrents. Rocks are mainly sandstone, with loose conglomerate beds in the upper strata. Soils are generally poor and infertile, with accumulation of humus in only a few places.

Climate: The three main seasons in the Himalayan foothills are: winter, summer and monsoons. The best time for a safari or a bird watching trip is during winter (November to February) when the days are pleasant (20-25*C), nights cold and humidity is low. Temperature rises rapidly to 40-48*C in the hot season (March to June) and rainfall increases with the occasional thunderstorm. Humidity is high in the rainy season (July to October), with over 750 mm of precipitation in July to August, and there is little temperature variation. Annual rainfall ranges from 1200-1500 mm.

Birds: Over 300 species have been recorded in Rajaji; notably Black-chinned Babbler, Rusty-cheeked Scimitar Babbler, White-crested Laughingthrush, Golden-spectacled Warbler, Chestnut-tailed Starling, Brown Hawk-Owl, Wallcreeper, Velvet-fronted Nuthatch, Chestnut-bellied Nuthatch, Black-crested Bulbul, Indian Pitta, Fire-capped Tit, Himalayan Flameback, Kalij Pheasant, Crimson Sunbird, Black-throated Sunbird, Fire-breasted Flowerpecker, Pale-billed Flowerpecker, White-rumped Shama, Rufous-bellied Niltava, Grey-winged Blackbird, Chestnut-headed Bee-eater, Lineated Barbet, Orange-bellied Leafbird, Golden-fronted Leafbird, Green Magpie, Peregrine Falcon, Drongo Cuckoo, Jungle Prinia, Brown Dipper, Rusty-flanked Treecreeper, Great Hornbill etc.

Fauna: Rajaji is important as the western limit of Asian Elephant (Elephas maximus). Other mammals recorded in Rajaji include Rhesus Macaque (Macaca mulatta), Langur (Presbytis entellus), Golden Jackal (Canis aureus), Sloth Bear (Melursus ursinus), Striped Hyena (Hyaena hyaena), Leopard (Panthera pardus), Tiger (P. tigris), Wild Boar (Sus scrofa), Muntjac (Muntiacus muntjak), Spotted Deer (Cervus axis), Sambar (C. unicolor), Nilgai (Boselaphus tragocamelus) and Goral (Nemorrhaedus goral). Some species have become locally extinct, notably Dhole (Canis alpinus), Mugger (Crocodylus palustris) and Gharial (Gavialis gangeticus).

Flora: About 84% of the national park is forested. Some 65% of forested land is under 20% crown cover in Rajaji range, whereas a similar percentage of forested land exceeds 50% crown cover in Motichur range. Canopy cover is intermediate for forests in Chilla. Of the five vegetation types of the Shivaliks, four occur in Rajaji, namely: moist Shivalik Sal (Shorea robusta), dry Shivalik Sal, northern dry mixed deciduous and Khair (Acacia catechu), Sissu (Dalbergia sissoo) forest.

Status: The area has traditionally been inhabited by Gujars (pastoralists). They herd buffalo between high Himalayan pastures in summer and lower foothills in winters. There are over 100 Gujar settlements within Rajaji range. Gujars are now in the process of being resettled. Some studies however suggest that the Gujars may not have a significant detrimental effect on the habitat. Rajaji has had problems of deforestation, soil erosion and poaching. Rajaji National Park harbors a significant Asian Elephant population, hence the proposal to link Rajaji with Corbett National Park by means of elephant corridors. This involves the construction of two special bridges over the Chilla Power Canal and the protection of intervening forest habitat.