What temperature to set your thermostat during summer heat wave?

Millions of Americans are facing hot, humid temperatures at the start of summer.

Across the Midwest and Northeast, over 40 million Americans are under extreme heat watches on June 20. Some states could reach into the 100s with high humidity. New York and Washington, D.C., could see temperatures surpass 90 degrees for up to a week.

For people with air-conditioning, window units and central air will be humming for days on end. While staying safe and staying cool is paramount, people must also balance their bills.

Here are tips to efficiently cool homes at the start of a scorching summer.

Hot and humid: Heat advisory for millions as 'dangerous' temperatures kick off summer