Windproof will get you there. Thick mittens that let wind squeeze through will chill your hands normally, and if your hands perspire like mine do after enough physical exertion, the wind will make them feel like frozen hell.
My hands are pretty good down to a lot colder than I'd expect with gloves that are hardly insulated but good at blocking wind. My snowboard gloves are too warm, ironically (at least at temps above 20F or so).