Whoa - that looks like an exciting journey to take !
There are direct flights but no direct trains for this journey. New Delhi (Delhi) to Port Blair (Andaman And Nicobar Islands) distance is 2479 km and you can get there by flight in just over 4 hours and 30 minutes or by train + flight fares starting from ₹ 4139.
The temperatures at this time of the day are in a comfortable range.