The state, which is facing flood and drought at the same time, is likely to receive light to heavy rainfall from September 1 to 4. Weathermen are expecting showers owing to a favourable position of the monsoon trough line.

Trough line is an imaginary contour connecting the points of low-pressure across the breadth of the country during the monsoon and monsoon rainfall normally hinges on it. While the main trough line was oscillating between Bihar and Jharkhand on Tuesday, the secondary one had also formed between eastern Bihar and the Gangetic Bay of Bengal.

"We have issued a warning for isolated heavy rainfall in eastern Bihar from August 1 to 4. The remaining places in Bihar, including Patna, are expected to receive light to moderate rainfall during the same period," said Arpita Rastogi, a Met scientist at Patna meteorological centre.

Arpita said the main trough line has stretched between two upper air cyclonic circulations, western Uttar Pradesh and west central Bay of Bengal, on Tuesday.

The showers are also expected to bring respite to people in Bihar from the soaring mercury over the past few days. The maximum temperature is being measured 3-6 notches higher than the corresponding normal for the past few days.

"The cloud cover would prevent the solar rays from directly reaching the earth's surface. Thus, we expected the maximum temperature to drop by 5-6 degrees Celsius over the next few days," said a senior weatherman at Patna.

Rain summary

Meteorologists are expecting a recovery in monsoon rainfall deficiency in Bihar owing to showers expected over the next few days.

As on date, 22 districts have received deficient rainfall this monsoon (-19 per cent and above), while 16 districts have received normal rainfall (+/-19 per cent).

The rainfall deficiency in Bihar stands at 21 per cent despite flood situation in a dozen districts.

Bihar is on the verge of a meteorological drought if monsoon doesn't make a recovery in September. Meteorological drought is declared in a state when the precipitation deficiency is 30 per cent or above.

The Met office has, however, not issued any forecast for the expected rainfall in September.

"Our headquarters has still not issued any monthly forecast for rainfall expected in September for Bihar or the entire eastern zone," said Arpita.

The monsoon officially arrived in Bihar on June 17 after a delay of seven days from its expected onset date and reached Patna by June 19. The rainfall deficiency for the period of June 1 to July 31 stood around 7 per cent this year.

The rainfall in July was four per cent excess of the corresponding normal for the month.

The recovery in monsoon rainfall figures started from around July 20, when the monsoon trough line shifted to the foothills of the Himalayas.

However, the state was left disappointed with regard to the monsoon rainfall in August because apart from a couple of spells of light showers, there was hardly any rainfall in most parts of the state.

As a result, the rainfall deficiency soared from 7 per cent by July-end to 21 per cent by August-end.

Such a situation prevails in the state despite the fact the rainfall deficiency in the country is mere 3 per cent during the same time. The country received 652.1mm rainfall between June 1 and August 25, against the corresponding normal of 670.9mm, leading to a deficit of 3 per cent.