Siwan district is mainly a plain and fertile agricultural land. It has highest temperature in May and lowest temperature in January. The highest Rainfall period is August and September. In summer it often faces cyclones.
Plants and Herbs:-
First of all Mr. M.H. Hens who was then forest conservator collected plants but Siwan district does not appear in his articles. At that time it was a Sub-Division of the Saran District.The land of Siwan cannot be divided into botanical zones.
Crops are cultivated in the district as per the seasons.There are mainly two major crops i.e. Khariff and Rabi.
January-March: - During this period mainly Kidney beans and summer paddy is grown.
Vegetables:-Vegetables are grown according to seasons.
Winter season :Potato, Cauliflower, Cabbage, Reddish, Spinach, Carrot, Brinjal, Tomato, Bottle gourd, Pumpkins etc are grown in this season.
Rainy Season: Ladyfinger, Bitter gourd, “Ghewara” etc are grown during this season.
Khariff: Its period is June to September and the main crops are Maize, Paddy, Sugarcane, and Millet etc.
Rabi: Its period is October to March and the, Main crops are Wheat, Grams, Peas, Mustards, Soya beans, Sunflower etc
The district has no forest area. The trees that are found in orchards and roadsides are Mano, Litchi, Eucalyptus, Pipal, Banyan, Neem, Ashok, Coconut etc.
The flowers that are found are Rose, Fern and Cactus, various types of Croton,Jasmine,Lily, Christhemum etc.