Far from being a quiescent time, the Phoney War (also known as "The Twilight War" and "Sitzkrieg" (literally, "sitting war")) was a term coined by American Senator William Borah (1865-1940) and refers specifically to the time between the Invasion of Poland and the Battle of Britain in the West. However, between the conquest of Poland and the air war over England, the rest of the world did not remain idle -- the Soviet Union invaded Finland and conquered the Baltic Republics. In the East, China continued its "War of Resistance" against Japan, which had invaded that country in the mid 1930's. Germany had ramped up war production in the 1930's and was indeed ready for a big war, namely, the conquest of the Soviet Union. Hitler's reasons for not prosecuting the war in force against France and England at this time had less to do with the weather, and more to do with his ultimate concern, the destruction of the Soviet Union. England, France, and Poland were but minor theatres of conflict.
This period, that lasted from October of 1939 to May of 1940, was not particularly significant. It simply represented a time when neither the British and French, on the one side, or the Germans on the other did any serious fighting on the land. The Phony War served as a time for both sides to get ready for a war that they had not really expected to have.
Hitler had expected that the Allies would not declare war on him when he invaded Poland in September of 1939 so Germany was not ready for a big war. The British and French had not expected Hitler to invade Poland, so they were not ready either. For this reason (and because winter makes fighting more difficult), neither side attacked the other during this time. Instead, they simply stayed where they were and tried to prepare for a broader war that would start later.