During this period the climatic conditions changed greatly. At the beginning of the Archaic period, the glaciers were retreating northward. The climate was not as cold as during the Paleo times but was colder and moister than today. Oak, hickory, and maple forests replaced the evergreens. A large quantity and variety of plants and animals were present.
During the middle of this period the temperature became warmer and dryer than today. Prairies expanded into areas that are now covered with forests. Some areas had active sand dunes that were shifting across the land, just like those that are found in the deserts of the southwest today.
At the end of the period the temperature became similar to what we are familiar with today. Water levels on Lake Michigan also fluctuated greatly during this time. Sometimes the lake levels were higher than today, and at other times they were lower. Rising lake levels have left some Archaic sites under water.