I'll be going camping in 7 days in 1000m elevation, with temperatures ranging from 15 to 7 celcius and the possibility of raining.

My friends are experienced campers and have camped without an actual tent in sub 5 celcius in a similar mountain. However, I forced them not to fuck around this time and we're getting tents.
Will a simple summer tent with 1000mm rain resistance keep me healthy, along with the necessary clothing, or will I have to buy something more mountaineer styled? I've never done this before and I feel somewhat overwhelmed. Got tips apart from the tent?
We'll have a car, so weight isn't a point of concern