Nearly 100 people have died since Wednesday after heavy rain lashed parts of India and Nepal, officials and media said, and the weather department has predicted more unseasonal rain for the region.

The Indian Meteorological Department (IMD) had on Wednesday raised a multi-hazard warning for the country, with heatwave conditions in the western parts and thunderstorms in the eastern and central region.

In the eastern state of Bihar, at least 64 people died in rain-related incidents since Wednesday, a senior official from the state's disaster management department told Reuters.

Local media reported that more than 20 people have died in India's most populous state of Uttar Pradesh.

Meanwhile in neighbouring Nepal, lightning strikes and heavy rain killed at least eight people, National Disaster Authority officials said.

India's weather office expects heavy rain with thunderstorm, lightning and gusty winds over central and eastern India till Saturday.

The monsoon season usually begins in June in southern India, and summer months in the recent past have been marked by intense heatwaves that have killed several people.

State-run IMD said last week that India is expected to experience a much hotter April, with above normal temperatures across most of the country.