The setting of small fires was a common way to clear forest land for farming and railroad construction. On the day of the Peshtigo fire, a cold front moved in from the west, bringing strong winds that fanned the fires out of control and escalated them to massive proportions. A firestorm ensued. In the words of Gess and Lutz, in a firestorm "superheated flames of at least 2,000 degrees Fahrenheit ... advance on winds of 110 miles per hour or stronger. The diameter of such a fire ranges from one thousand to ten thousand feet ... When a firestorm erupts in a forest, it is a blowup, nature's nuclear explosion ... "