Most astronomy sessions are run at night, in the dark (Surprise Surprise)
And at night it gets cold, so there are a few things you need to do to keep your most important piece of observing gear (you!) in tip-top condition.
Keep yourself warm. wear layers of clothing that you can add as the temperature drops and yet remove if it warms up. Try not to get too warm and sweaty at the start of a session, that will only make you colder later on.
Make sure you have a good, thick sole on your boots and thick socks to keep your feet warm. I find that once my feet are cold, I’m done-for.