Diesel sales by Indian state-run retailers dropped in the first half of September compared to August, according to preliminary data released Monday, as monsoon rains slowed industrial activity and transportation. Typically, fuel demand in India, the world’s third-largest oil importer and consumer, declines during the monsoon season, which starts in June and brings heavy flooding to parts of the country.

Diesel sales, mostly used by trucks and commercial vehicles, reached 2.4 million metric tons, down 4% from August and 12.3% lower than the same period last year. Gasoline sales, used primarily in passenger vehicles, remained flat at 1.23 million tons but dropped 5.1% year-on-year. Monsoon rains also reduced agricultural demand for gasoil-powered irrigation generators.

Indian Oil Corp, Hindustan Petroleum Corp Ltd, and Bharat Petroleum Corp Ltd, which control about 90% of India’s retail fuel outlets, saw a slight 3.3% monthly increase in liquefied petroleum gas (LPG) sales, though sales were down 2.9% from last year. Aviation fuel sales dipped 1.1% from August, reaching 303,600 tons.