A Nor'wester alert has been sounded for the weekend, a respite many were looking for in the hot and dry conditions prevailing for the past few days.

Patna and other parts of Bihar are expected to witness a Nor'wester - sudden thunderstorm activities during summer - over the next three days. This would be the second Nor'wester in the week, following the thunderstorm on Monday, which had led to night-like conditions in the afternoon.

Weathermen claimed that the formation of dense cloud would start over most parts of the state by Saturday evening, followed by thunder and mostly high-intensity squalls amid light rain on Sunday and Monday. Temperature, on the other hand, is expected to drop by 4-5 notches during peak Nor'wester activities, which normally do not last for more than two hours. Accordingly, the local Met centre has forecast the maximum temperature in Patna to drop down from 37.1 degree Celsius recorded on Friday to 32-33 degree Celsius on Sunday and Monday.

The expected change in weather conditions has been attributed to change in wind direction from dry westerly to moist easterly. The ongoing high-temperature conditions would also support the Nor'wester.

"The easterly winds from China Sea, which caused the Nor'wester earlier this week, are expected to revive in the region by Friday night. When the moisture brought by the winds comes in contact with the prevailing high-temperature conditions in the state, it would lead to thunderstorm," said Ashish Sen, director at Patna meteorological centre.

Excess heating of the land during summer results in convective currents that in turn help in the formation of low cumulonimbus clouds, bringing rain accompanied by gusty winds, brewing a typical Nor'wester. The Nor'westers hitting Bihar normally originate from the Chhotanagpur plateau region, when air over the plateau heats and gains altitude with moisture support from an anti-cyclonic circulation or similar weather in China Sea or Bay of Bengal.

Patna meteorological centre chief claimed that the expected Nor'wester activity during the weekend would not bring much rain to the state.

"The level of moisture to be brought by the easterly winds is not expected to be very high. Thus, the possibility of high-speed gusty winds or squalls is much higher than that of typical heavy rain during thunderstorm," said Sen.

The Met chief added that wind speed would be comparatively higher if there is thunderstorm either in the afternoon or evening. During the thunderstorm witnessed on Monday afternoon, the wind speed was measured at 70-80kmph.