ains ▁to ▁Chen na i ▁. ▁ ▁T amil ▁N adu ▁has ▁rain ▁during ▁the ▁mon so on ▁season ▁due ▁to ▁the ▁south west ▁trade ▁wind s ▁which ▁blow ▁towards ▁the ▁northern ▁hem is phere . ▁T amil ▁N adu ▁receives ▁ra inf all ▁in ▁the ▁winter ▁season ▁due ▁to ▁n ortheast ▁trade ▁wind s . ▁The ▁normal ▁annual ▁ra inf all ▁of ▁the ▁state ▁is ▁about ▁ 9 0 7 ▁( L PA ▁ 1 9 5 0 - 2 0 1 9 )   mm ▁( 3 7 . 2   in ) ▁of ▁which ▁ 4 8 % ▁is ▁through ▁the ▁North ▁East ▁mon so on , ▁and ▁ 3 2 % ▁through ▁the ▁South ▁West ▁mon so on . ▁Since ▁the ▁state ▁is ▁entirely ▁dependent ▁on ▁ra ins ▁for ▁re charg ing ▁its ▁water ▁resources , ▁mon so on ▁fail ures ▁lead ▁to ▁ac ute ▁water ▁scarc ity ▁and ▁severe ▁dr ought . ▁ ▁T amil ▁N adu ▁is ▁class ified ▁into ▁seven ▁ag gro - cl im atic ▁zones : ▁north - east , ▁north - west , ▁west , ▁southern , ▁high ▁ra inf all , ▁high ▁alt itude ▁h illy , ▁and ▁C au very ▁D elta ▁( the ▁most ▁fert ile ▁agricult ural ▁zone ). ▁ ▁Statistics ▁ ▁Tem per ature ▁ ▁P reci p itation ▁ ▁Des ert ▁So il ▁ ▁Most ly ▁desert ▁so ils ▁seems ▁around ▁Mad ur ai ▁, ▁Vir ud h un agar ▁, ▁S iv ag anga ▁, ▁Ram