Earlier quoted context omitted.
The real game changer is a helmet with a full face visor. Also I am warmer on a scooter than a bike due to the fact that I'm not moving my legs "pumping" air in and out of my clothes. I found that on an electric scooter with a full helmet I was totally warm at high speed into icy wind coming off the sea. Warmer than say just standing outside for a few minutes with a hat and scarf but my face not covered.
Do you mean scooter as a standing one or as motorbike
Standing on one, but really I think the main point is you aren't peddling. My legs would absolutely freeze riding a non-electric bike, each rotation of the peddles as your knee flexes all the warm air is forced out of your pants and then cold air is sucked in as you straighten your leg at the bottom. At least this was the case for me with jeans. I would do ~25mph on a fold-up type scooter in the same weather, just adding the full visor helmet, and didn't feel even slightly cold.