My standard leggings are Icebreaker merinos at 260 wt---fairly heavy wt. See pic. This is my standard cold weather bottoms---shorts over leggings. Or just shorts and bare legs.
In a cold rain there's no way I'll be using my merino leggings in any capacity except for in-camp living and sleeping. They stay dry at all costs. Instead I'll either hike in shorts or my rain pants over my bare legs to keep me warm---and I often put the shorts over the rain pants so I'll have pockets for various on-trail items. See bottom pic---me on left.
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Trip 187 (231)-XL.jpg
In a cold rain there are a few items which are allowed to get soaking wet---my boots/socks, my shorts, my rainpants/rain jacket---and minimal baselayers underneath the rain jacket. In camp all these items are striped off and replaced with dry layers including merino leggings.
In the morning all the wet stuff is put back on so nothing ever gets "more wet" as the trip continues. The wet stuff gets "walked dry" eventually. Minimal torso baselayers under the rain jacket are a long sleeve silk top and a poly t-shirt over the silk---for a cold rain. The GTX jacket supplies the necessary core heat. In real cold with no rain alot more torso layers can be worn under the rain jacket---and pace slowed to prevent sweating.