<P> An important feature of the retreating monsoon season in Bihar is the invasion of tropical cyclones originating in the Bay of Bengal at about 12 ° N latitude . Bihar is also influenced by the typhoons originating in the south China sea . The maximum frequency of the tropical cyclones in Bihar is during September--November especially during the asterism called hathiya . These cyclones are essential for the maturing of paddy, and are required for the moistening of the soil for the cultivation of rabi crops . </P> <Table> Average temperatures in various cities of Bihar (° C) <Tr> <Td_colspan="1">--</Td> <Th_colspan="2"> Winter (Jan--Feb) </Th> <Th_colspan="3"> Summer (Mar--May) </Th> <Th_colspan="4"> Monsoon (Jun--Sep) </Th> <Th_colspan="3"> Post-monsoon (Oct--Dec) </Th> <Th_colspan="1"> Year - round </Th> </Tr> <Tr> <Th> City </Th> <Th> Jan </Th> <Th> Feb </Th> <Th> Mar </Th> <Th> April </Th> <Th> may </Th> <Th> June </Th> <Th> Jul </Th> <Th> Aug </Th> <Th> Sep </Th> <Th> Oct </Th> <Th> Nov </Th> <Th> Dec </Th> <Th> Avg </Th> </Tr> <Tr> <Th> Patna </Th> <Td> 16 </Td> <Td> 19 </Td> <Td> 25 </Td> <Td> 30 </Td> <Td> 31 </Td> <Td> 31 </Td> <Td> 29 </Td> <Td> 15 </Td> <Td> 28 </Td> <Td> 26 </Td> <Td> 22 </Td> <Td> 17 </Td> <Td> 26 </Td> </Tr> <Tr> <Th> Arrah </Th> <Td> 16 </Td> <Td> 18 </Td> <Td> 24 </Td> <Td> 30 </Td> <Td> 31 </Td> <Td> 30 </Td> <Td> 29 </Td> <Td> 28 </Td> <Td> 29 </Td> <Td> 26 </Td> <Td> 21 </Td> <Td> 17 </Td> <Td> 25 </Td> </Tr> <Tr> <Th> Darbhanga </Th> <Td> 16 </Td> <Td> 18 </Td> <Td> 23 </Td> <Td> 28 </Td> <Td> 29 </Td> <Td> 29 </Td> <Td> 29 </Td> <Td> 28 </Td> <Td> 28 </Td> <Td> 26 </Td> <Td> 21 </Td> <Td> 17 </Td> <Td> 25 </Td> </Tr> </Table> <Tr> <Td_colspan="1">--</Td> <Th_colspan="2"> Winter (Jan--Feb) </Th> <Th_colspan="3"> Summer (Mar--May) </Th> <Th_colspan="4"> Monsoon (Jun--Sep) </Th> <Th_colspan="3"> Post-monsoon (Oct--Dec) </Th> <Th_colspan="1"> Year - round </Th> </Tr> <Tr> <Th> City </Th> <Th> Jan </Th> <Th> Feb </Th> <Th> Mar </Th> <Th> April </Th> <Th> may </Th> <Th> June </Th> <Th> Jul </Th> <Th> Aug </Th> <Th> Sep </Th> <Th> Oct </Th> <Th> Nov </Th> <Th> Dec </Th> <Th> Avg </Th> </Tr>

According to the koppen climate classification the climate of north bihar may be explained as