battery

My daughter had the car turned off but had the power running to the radio while she waited for someone, don't know how long. She stated the min on the cd faded and quit, tried to start the car it clicked several times and would not start. Triple A came the car then started. Do you think she ran the battery down just listening to the radio without the engine running? and is it possible to run down the battery by doing what she just did. The weather has been awlful hot this last week does that have an impact on the battery of the car. It has been running fine the past few days