Ummmm - lack of sun??? It is still Spring? But most importantly just because global warming is happening it does not mean that we will never see another cold day
During the night heat is lost, so that when the sun rises it is about the coldest part of the day. The sun then starts heating the ground. The above is a simplistic explanation. It ignores clouds and other factors.
That's the answer, defy entropy, a lot better then oxidising carbon to generate a potential difference which can be used to generate heat.