Take the back roads, at stop signs when nobody is around, or stop lights when you have a long red, get off the bike and do pushups until the crossing lane's light turns yellow. You should be able to get at least 30 in.
Then feel the warmth spread as you ride to the next one...
It got me through some seriously cold days before I learned to be prepared.
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My therapist has 2 wheels and a seat.
If you are ever in doubt to my tone, please refer to my avatar.