Iowa averages about 50 days of thunderstorm activity per year.
Iowa summers are known for heat and humidity, with daytime temperatures sometimes near 90 °F (32 °C) and occasionally exceeding 100 °F (38 °C).
More than 3,000 years ago, during the Late Archaic period, American Indians in Iowa began utilizing domesticated plants.
The subsequent Woodland period saw an increased reliance on agriculture and social complexity, with increased use of mounds, ceramics, and specialized subsistence.
The southern border is the Des Moines River and a not-quite-straight line along approximately 40 degrees 35 minutes north, as decided by the U. Iowa's bedrock geology generally increases in age from west to east.
In northwest Iowa, Cretaceous bedrock can be 74 million years old; in eastern Iowa Cambrian bedrock dates to c. Northeast Iowa along the Upper Mississippi River is part of the Driftless Area, consisting of steep hills and valleys which appear almost mountainous.
Other factors negatively affecting Iowa's environment include the extensive use of older coal-fired power plants, Iowa has a humid continental climate throughout the state (Köppen climate classification Dfa) with extremes of both heat and cold.