The fire, which began June 23 and has consumed 18,500 acres, has forced about 32,000 people from their homes in and around Colorado Springs, The Denver Post reported.
"We know hundreds of homes have been destroyed," Bach said.
President Obama planned to travel to Colorado Springs to view the damage Friday.
The U.S. Air Force Academy near Colorado Springs said it evacuated about 550 cadets away from the academy's campus, including about 200 summer academics cadets relocated to the University of Colorado, Colorado Springs campus.
"UCCS has been a terrific partner helping our faculty and cadets continue our academic programs while we focus on the Class of 2016 and in-processing," said Brig. Gen. Dana Born, dean of faculty.
The airmanship program and other training programs also were postponed, and 350 cadets were released to local sponsor families, the academy said on its Web site.
As of Wednesday evening, no structures on the academy campus were threatened by the Waldo Canyon Fire, the Web posting said.
Before the evacuation of the cadets was announced, the academy ordered the evacuation of several housing areas "as a health and safety precaution resulting from the unpredictability of the fire."
The academy was closed to visitors.
The fire was about 5 percent contained, an incident report posted by InciWeb.org indicated. The FBI is helping local authorities determine what started the blaze.
InciWeb.org said 20,085 homes and 160 commercial building are threatened.
Firefighting efforts as of Thursday were estimated at $3.2 million, officials said.
Fire officials said higher humidity levels, rain and diminished winds helped firefighters Wednesday, the Post said.
"Yesterday was a good day to make some headway," U.S. Forest Service supervisor Jerri Marr said.
A stretch of U.S. 24 near Cave of the Winds would remain closed through the weekend, officials said. Major tourist attractions Garden of the Gods and the Pikes Peak Highway and cog railroad were closed to visitors.
Officials said mandatory evacuation orders were in effect for the communities of Cascade, Chipita Park Green Mountain Falls and Crystola; portions of northwest Colorado Springs, the Air Force Academy and unincorporated Teller County.
Incident commander Rich Harvey called Wednesday "a good day" for firefighters and said crews would be "incredibly aggressive" Thursday, the Post said.
Temperatures were expected to be in the upper 90s F Thursday after hovering around 100 since the fire broke Saturday.
A thousand firefighters battled the blaze, one of four major fires burning in Colorado. Dozens of other forest fires burned across the West.
The White House said President Barack Obama would tour the affected area Friday.