Jamestown was easily defensible, as it was located on a peninsula with a thin isthmus connecting it to shore. It was surrounded by water on three sides, including the Back River, James River, and Sandy Bay, and was located near a deep harbor. Surrounding Jamestown were hardwood forests and tidal, marshy wetlands. It was not easy to find sources of fresh water in the area.
According to the NASA source below, Jamestown was subject to hot summers with high humidity, mosquitoes, and other bugs. Historians believe that during the time Jamestown was established, North America was going through a "Little Ice Age" that brought severely cold winters. In addition, as the source below explains, a study of tree rings in the area shows evidence of a drought at the time Jamestown was established, and the sandy soil was not conducive to growing crops. As a result, the colonists in Jamestown endured what is now called "The Starving Time" in the winter of 1609-1610. It was not until the colonists began to plant tobacco that the colony became more tenable.