A red alert denoting severe heat wave has been issued for six districts of Karnataka by the Karnataka State Natural Disaster Monitoring Centre (KSNDMC), as temperatures are likely to cross 46 degrees Celsius.Bagalkote, Belagavi, Dharwad, Gadag, Haveri and Koppal districts will see temperatures ranging from 40 to 46 degrees Celsius between May 1 and May 9, according to KSNDMC.