Coolant leaking from Heater core drain tube

Car is losing coolant and it is creating a small puddle under the car. I have tracked the leakage problem to the heater core drain tube. I need to know what the problem is. Do I need to replace the heater core? Is it normal to have coolant drain from that hose? The heater core drain hose, (I think that is what it is called), is located on the rear lower left firewall as your looking from the front of the care, next to the A/C input and output lines. This problem started about 3 weeks ago, could it be related to the high temperatures we been having?

Thanks,

Jim