If you live in the central or eastern U.S., it’s time to fill your ice trays and seek shade as a major heat wave will put 50 million Americans under a heat warning this week.

People in Nashville, Chicago, Kansas City, Philadelphia, New York, Washington, D.C. and many other cities will be fanning themselves as temperatures top 95 degrees. High humidity will intensify the effect. “The prolonged duration of the heat and humidity will potentially become dangerous to those most vulnerable,” the National Weather Service warned. The heat wave will probably last at least three days.

Related: Heatwave roasts mussels alive in California

Climate scientists predict that by the mid-21st century, Americans will face an average of 36 days annually when the heat index surpasses 100 degrees, and 24 days when it exceeds 105. By 2100, those numbers could rise to 54 and 40.

“Our analysis shows a hotter future that’s hard to imagine today,” said UCS senior climate scientist Kristina Dahl, according to Newsweek.

In addition to direct health risks of scorching weather, heat waves bring other dangers and inconveniences to cities. More people cranking air conditioners lead to power fails. Places like Manhattan— which is served by underground delivery systems that heat up as the ground gets hot— are especially susceptible to blackouts.

Scientists predict that the current heat wave will bring record high overnight lows in many cities, and that this pattern will also continue to rise with climate change. This phenomenon presents a serious health risk, as people’s bodies don’t have a chance to cool overnight.

Via EcoWatch

Image via NASA Earth Observatory