It's factory sealed with O-rings. Any Pentax lens with a WR (Weather Resistant) designation is. You can't submerge it but I have used mine in pouring rain with no problems. That kit lens is WR I'm pretty sure. As is my 18-135 and any of the current DA * (star) line of lenses and a few of the DA lenses (the 18-250, 50-135, 60-250, 200, and 300 come to mind off the top of my head).
I kind of lust for the DA* 300mm f/4 and the DA * 60-250 f/4. One day...