I don't want to tell my boyfriend about the snow.
That seems strange. Why aren't you going to tell him about the snow?
He doesn't drive, so he doesn't understand how the snow affects driving conditions and that is why I am late. 
Not being honest with partners can cause mistrust. You are assuming he won't understand, but you don't know that for sure. I think it would be easier if you were honest and explain it to him in detail.
I just don't want to confuse him and have him nagging me 24/7.
But that is how he will learn. Otherwise, if you are not truthful, he will never know how to see things from your perspective and will have a hard time trusting you in the future.