Yes, unless I'm absolutely sure that no snow is adhereing to my critical surfaces. I'd ensure that by doing a tactile check of the critical surfaces during the preflight, and perhaps an optional contamination check from the cabin windows at the hold short just prior to takeoff.
I don't subscribe to the "it'll blow off during the takeoff roll" theory that I read on the Internet form time to time. If it's adhering during preflight or taxi, I don't think you can just assume that it's going to blow off during the takeoff roll. In fact it's even written into our FOM "Pilots may not assume that snow will blow off during takeoff". If it's that cold (-9), I don't see how you wouldn't be accumulating some snow on the wings (although I guess it's possible), and if you're flying a jet without slats, you're especially susceptible to performance degradation.
So I have to say I'd probably de-ice with type I, assuming I could get out of there within the holdover time for -SN, otherwise I'll take some III, or I + IV. They only exception would be if the snow was falling in some way that it wasn't adhereing to the aircraft, or was melting on contact. I don't see how that could happen at -9 though.
Maybe that makes me overly conservative, but that's the way I interpret the rules.