S Balachandran of Chennai Meteorological Centre has explained the above questions. He said As per the astronomy it has been mentioned that when Agni Natchathiram will begin and when will it end. This year the Agni Natchathiram has begun on 4th May and will end on 28th May. As per astronomy, the heat has continued many years even after the Agni Natchathiram. It is no where mentioned about Agni Natchathiram or Kathri Veyil in the weather department. It is the usual hot summer of the May. After getting the information about the weather, we ready a map and forecast according to the weather rules.
Normally May is a hot month. Because of this there will be convection. The sun rays falling on the earth warms the air. The wind expands because of this it loses its velocity. If there is convection in the air, there will be rains.