Geography of Basti District in Uttar Pradesh includes two main river systems namely, the Ghaghara River and Rapti River, both of which ultimately form a part of the great Gangetic system. The other streams of the district are the Kuwana, its tributaries are, Rawai and Katnehia, and Ami is a tributary of Rapti. In spite of its apparent uniformity of aspect, topographically Basti District is divided into several distinct tracts namely, the low valley of Ghaghara River in the south, extending from that river to its tributary, the Kuwana; the central upland, between Kuwana river and Rapti river; and the low and ill-drained paddy belt between the Rapti and the Nepal boundary.

River Ghaghara forms the southern boundary of the district, from its entry opposite the sacred town of Ayodhya, where for a short distance it is usually known as the Saryu. During the rains it carries immense volume of water, but in dry weather it shrinks considerably. This river has a constant tendency to change its course during the floods, and in this manner large tracts of land from time to time are transferred either to the northern or southern banks, rendering the total area of the district subject to incessant variation. These changes have occasionally been accompanied by the formation of large islands and deep stream rule prevails, the constant shifting of the jurisdiction of such lands from one district to another results in considerable inconvenience. Kuwana River rises in the low ground in the east of Bahraich District and first touches the district in the stream west of Rasulpur.

The climate of Basti District is more equable than the adjoining districts to the south. The year may be divided into four seasons. The winter season, from mid-November to February is followed by the summer season lasting till the middle of June. The period from mid-June to the end of September constitutes the south-west monsoon season. October to mid-November is the post monsoon or transition period. The average annual rainfall in the district is 1166 mm. During the winter season the mean minimum temperature is about 9 degree Celsius and the mean maximum temperature is 23 degree Celsius while during the summer season the minimum temperature is about 25 degree Celsius and the mean maximum temperature is about 44 degree Celsius. In the south-west monsoon and the post monsoon seasons the relative humidity is high, being above 70 percent. Thereafter the humidity decreases and summer season is very dry.

In the past a large part of the district was covered with forest of Sal and other trees, but since then most of it has been cleared and brought under the plough. However, plantations of fast growing species such as bamboo, Eucalyptus and mango have been raised in the district.