The United States is currently experiencing a brutal heatwave, with 195.7 million people under either an excessive heat watch, warning or heat advisory on Friday. Temperatures on Saturday will rise even higher in some areas.

The heatwave goes from the northeastern part of the country, such as states like New York and Massachusetts, to states further west like Missouri and Kansas. The heatwave also affects eastern parts of Canada, such as the province of Quebec and the major city of Toronto.

Temperatures will be in the mid to upper 90's in many areas, but the humidity will make it feel even warmer. In Washington, D.C., the nation's capital, the temperature will be around 98 degrees Fahrenheit, yet will feel like it is 115 degrees.

In New York City, Mayor Bill de Blasio has ordered landlords to turn down the air conditioning to 78 degrees in office and apartment buildings to conserve energy during the heatwave. New York authorities fear that air conditioning could put a strain on the city's resources. 

Being out in the warm weather without staying hydrated can lead to heat exhaustion. Heat exhaustion results in heavy sweating and a rapid pulse. High humidity makes it especially deadly, as human sweat won't dry on the skin, which would prevent the human body from cooling down. 

Authorities are urging citizens to stay inside and stay hydrated. The elderly and young children are particularly at risk during a heatwave.

Previous heat waves have been deadly. A 1992 heat emergency in Chicago killed approximately 692 people, with a total of more than 3,300 people going to the emergency room. 

Other parts of the world have also experienced a record high heatwave this summer. In June, France experienced its highest temperatures ever recorded, at 115 degrees Fahrenheit.