Basti’s climate is more equable than that of the adjoining districts to the south. The year may be divided into four seasons. Winter, from mid-November to February, is followed by summer, which lasts until approximately the middle of June. The period from mid-June to the end of September is the southwes t monsoon season, and october to mid-November is the post-monsoon or transition period.
During the monsoon season, and for brief spells of a day or two in winter, heavily clouded or overcast skies prevail. During the rest of the year the skies are mostly clear or lightly clouded.
The average annual rainfall of the district is 1166 mm.
During the winter season the mean minimum temperature is about 9°C and the mean maximum temperature 23°C. During the summer, the mean minimum is about 25°C and the mean maximum about 44°C.
In the southwest monsoon and post-monsoon seasons the relative humidity is above 70%. Thereafter the humidity decreases, and in the summer the air is very dry.
The winds are in general very light, with a slight increase during the late summer and monsoon seasons. The average annual wind speed ranges from 2.0 to 7.1 km/h.