One reason is because the short days and long nights prevent the earth from warming up, another reason could be because the sun's rays in winter are more spread out thus minimizing the amount of energy
For giving you understanding ; we need Free O2 but Oxygen is also available in H20 right why dont we use it !!
As the early atmosphere was reducing as there was no free oxygen but it was later produced by chemoautotrophic bacteria !! Living thing release O2 in atmosphere thus making it oxidising in nature and then life evolves !!
Weather changes every day, while climate changes annually or every 3 months
