Mayor Bill de Blasio and city commissioners urged New Yorkers to use common sense, seek out air-conditioning and check on neighbors Monday in the extreme heat, as temperatures hovered in the 90s.

"This kind of heat can be dangerous," de Blasio said at a news conference at Office of Emergency Management headquarters in downtown Brooklyn. "People have to make smart decisions. People, of course, have to stay hydrated. Don't stay out in the sun any longer than you have to."

An air quality alert is in effect until 11 p.m. Monday night, and people with respiratory illnesses should exercise caution, de Blasio said.

Office of Emergency Management Commissioner Joe Esposito added: "If we use common sense, I think we can get over this. This is not the day to go out there working on your tan."

Children and pets should not be out in the sun and humidity, and those laboring outside such as construction workers should use a "buddy system" to keep tabs on partners who may become heat-exhausted, Esposito said.

He said there have been no weather-related injuries or incidents and the few power outages have been resolved.

De Blasio said New Yorkers should call 311 with nonemergency concerns and call 911 for emergencies.

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He said air-conditioning should be set to 78 degrees.

Health Department Commissioner Dr. Mary T. Bassett said residents should take lukewarm showers to cool down and stay hydrated by drinking water.

Older New Yorkers and those with chronic illnesses are especially at risk of heat-related illnesses or even death, she said.

Signs of heat exhaustion include profuse sweating and clamminess, she said.