The Met office has issued a forecast for light to moderate rainfall over the next couple of days across Bihar following rain on the weekend because of the active southwest monsoon.

Though Bihar has been receiving good rainfall for nearly a fortnight, weathermen claimed that the southwest monsoon has started withdrawing from Rajasthan. According to the daily bulletin on Sunday issued by India Meteorological Department (IMD), the monsoon withdrawal line was passing through west Rajasthan.

Arpita Rastogi, a Met scientist and acting director at the Patna metrological centre, said the normal date of withdrawal of monsoon in Bihar is around October 10. However, sources said the weather office is expecting an early withdrawal.

Rastogi attributed the ongoing spell of showers to a secondary trough passing through the state.

"We are expecting showers over entire Bihar, with concentration over northwest, north-central, southwest and south-central parts of the state," she said. "A warning has been issued for heavy rainfall in the southwest and south-central parts of the state over the next 24 hours."

Patna, in south-central Bihar, experienced thundershowers and lightning on Sunday afternoon too.

Private weather agency Skymet has been reporting similar activities in Bihar and Jharkhand in the past few days. The agency stated that conditions are favourable for development of thunderclouds followed by thunderstorm activities in the eastern parts of the country, usually in the afternoon hours.

"Moist easterlies are prevailing in the lower levels and a trough is extending across the eastern parts of the country. These two weather systems are causing instability over the region," the Skymet report said.

Apart from welcome showers, weather in Bihar is expected to be soothing over the next few days.

IMD in its forecast has said Patna's maximum temperature is expected to be around 32-33 degrees Celsius in the next three-four days, while the minimum temperature will hover around 24°C.

Monsoon officially arrived in Bihar on June 17 after a delay of seven days, and reached Patna by June 19.

The frequent showers over the past fortnight, primarily in the southern parts, have significantly reduced monsoon rainfall deficiency.

Bihar's overall monsoon rainfall deficiency has come down to 21 per cent (on August 31) to 11 per cent on Sunday. Patna's rainfall deficiency stands at 16 per cent as of Sunday.