Outside the bedroom window

...is a rhododendron bush whose crimson blooms are long gone. In their place around this time every year a creeping vine displays its white blossoms, so the bush goes from red flowers to white in a matter of weeks. Anyone know what it is? It grows like a clematis, but doesn't have as many petals and is cone-shaped at its fullest, like this one. I think it might be some kind of flowering weed? Anyway, they make for a nice view in the morning. :)