Thermal underwear, fleece or wool sweater preferably a thin fleece and a wool sweater, wind/waterproof jacket, fleece pants, thick hat that you can really hide under, big thick gloves maybe two pairs cause it so boring when they get wet. Plus 2x pairs of woolen socks and snow/hike boots that are 1.5-2 nubers to big so you can get the socks on and not feel its too tight, toes need air and blood circulation. Weird extra tip if you start to freeze and everything seems normal, try go poop that is also a big heat drain.
Big boned and big furred is a common curse amongst house cats, ohh and big muscles hiding underneath the fur.