I have different gloves for every temperature range.

I have Pearl Izumi Infernos for seriously cold (below zero).

A few days ago I rode in 7 F temperatures wearing knit wool gloves with knit polyester gloves over them.

Two layers of knit gloves will work in remarkably cold weather IF they fit loosely enough.

Tight gloves won't keep your hands warm.
Loose gloves allow blood flow and airspace between the skin and the outside air.

Also, handlebars pull a lot of heat out of the hands.
It might help to double wrap them with tape in order to insulate your hands from the bars.

At the first sign of cold finger tips, swing your hands (one at a time) in an arc to force blood down into your finger tips.
Swinging my hands has made them warm on the coldest mornings imagineable.
Force that blood down into the finger tips.