Talks between Consolidated Edison and its largest union resumed Monday as another heat wave hits New York City.

The Con Ed workers were locked out on June 30 after their contract expired and negotiations over a new one failed. About 5,000 managers are keeping electricity going for 3.2 million customers in New York City and Westchester County

Neither Con Ed nor the Utility Workers Union of America Local 1-2 has indicated any real progress.

City cooling centers will be open for a second day Tuesday, as this brief heat wave hits its stride. Hot, humid weather with temperatures in the low 90s is expected through Wednesday.

National Weather Service meteorologist Dan Hoffman says this isn't the hottest heat wave and it won't be the last. “This particular heat wave, we're expecting a little bit more of a west wind so there probably will be a little bit more humidity for this heat wave, but humidity doesn't always increase with each heat wave so each one's a little bit different.”

Hoffman says it literally comes down to which way the wind blows. If wind comes down off the mountains it’s dry air, but if it comes up off the ocean it brings moist air.

Going into the third week of negotiations, there have been no major outages.

Union spokesman John Melia says the company "bowed to public pressure" in reinstating health insurance for the 8,500 locked-out workers. Workers are covered for July, retroactively.

Jenna Flanagan contributed reporting.