cold

Assalamu'alaikum dear scholars. I was on a bus trip a few month ago and it was cold. The bus stopped and my Muslim friends went out to the cold for ablution. Later, they ended up freezing. Is it supposed to be that hard to make prayers?And they chose to pray sitting in the bus without knowing the direction of Qiblah although they can pray standing and face Qiblah in a building. Were their prayers valid?Thanks in advanced.