ATLANTA, Feb. 1 — Cities should close schools for up to three months in the event of a severe flu outbreak, ball games and movies should be canceled and working hours staggered so subways and buses are less crowded, the federal government advised today in issuing new pandemic flu guidelines to states and cities.

Health officials acknowledged that such measures would hugely disrupt public life, but they argued that these measure would buy the time needed to produce vaccines and would save lives because flu viruses attack in waves lasting about two months.

“We have to be prepared for a Category 5 pandemic,” said Dr. Martin Cetron, director of global migration and quarantine for the Centers for Disease Control and Prevention, in releasing the guidelines. “It’s not easy. The only thing that’s harder is facing the consequences. That will be intolerable.”

In an innovation, the new guidelines are modeled on the five levels of hurricanes, but ranked by lethality instead of wind speed. Category 1, which assumes 90,000 Americans would die, is equivalent to a bad year for seasonal flu, Glen Nowak, a C.D.C. spokesman, said. (About 36,000 Americans die of flu in an average year.) Category 5, which assumes 1.8 million dead, is the equivalent of the 1918 Spanish flu pandemic. (That flu killed about 2 percent of those infected; the H5N1 flu now circulating in Asia has killed more than 50 percent but is not easily transmitted.)