could be warm or cold. Just bring blankets and maybe a portable heater. You may not even need them. But better to be safe than sorry. Jan is probably one of our coldest months. But the days will be beautiful.
Yeh it depends- the first trip my DH took me to the Fort- we tented it. It was so cold, even with a heater. But it was still fun and it's still a trip we talk about. Just make sure you have a nice warm sleeping bag and heater & you should be fine... and flannel PJs! (Zip 2 sleeping bags together and you'll stay warmer too!)
please make sure the heater is electric not combustion(gas/propane) also having a thermarest or nice air mattress will help keep your body heat traveling straight to the ground......