Capital Patna recorded a maximum temperature of 42.2 degrees Celsius, according to state Met office bulletin.
Bhagalpur and Purnea registered a maximum of 39.6 and 36.4 degrees Celsius respectively.
The weather will remain partly cloudy over the next 24 hours, the meteorological centre said.
It also forecast hot condition tomorrow as temperature would hover around 42 degrees in Patna.