Cold weather
Pitch your tent on a site sheltered from the wind. Keep the doors and air vents closed.
In extremely cold weather, a sleeping bag liner can be filled with dry leaves or hay and used as s mattress or a cover. The ground gets much colder at night, so you need plenty of protection under as well as over you.
Keep warm at night by wearing more clothes. Socks, underwear, a pullover and even a woolly hat will keep you warm in bed.