The rating means there is high COVID-19 community spread and pressure on the health care system in the city is substantial.
"New York City has transitioned to a high COVID alert level, meaning now is the time to double down on protecting ourselves and each other by making choices that can keep our friends, neighbors, relatives and coworkers from getting sick," said Dr. Ashwin Vasan, the city's health commissioner, Xinhua reported.
The guidance requires New Yorkers to wear a face mask in all public indoor settings and crowded outdoor settings and consider avoiding higher-risk activities.
New York City raised its COVID-19 alert level to "medium" from "low" in early May.
Even though there is only one step away to reach the highest COVID-19 alert level, New York City Mayor Eric Adams said on Monday, "We're not at the point of mandating masks."
The seven-day average percentage of positive COVID-19 test results rose to 5.18 percent in New York City on Monday, still the lowest among 10 regions in New York State, according to data issued by the state on Tuesday.
Daily new COVID-19 cases in the United States have been on the rise since early April, and the death toll from the pandemic has surpassed 1 million in the country.