I'll do a road ride in the high 30s wrapped up in a thin base layer covered by a winter weight outer layer faced with wind proof fabric. My ears must be covered, hands might be in two layers, and it's really important to keep the wind off my neck. It's possible to tootle around the lake trail or neighborhood in less technical gear.
I tend to go for slower speed activities when the temps dip into the 20's. Wind chill is exponential, and I have enough borderline frostbite damage to my extremeties as it is
. I, too, go bonkers having to stay in and miss my endorphin fix. I go running, and love to skate ski. Snow shoeing is good too
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The bicycle is the most civilized conveyance known to man. Other forms of transport grow daily more nightmarish. Only the bicycle remains pure in heart. ~Iris Murdoch, The Red and the Green