The first wave of strong heat this season extends from the five Great Lakes to the Atlantic, increasing electrical utilities demand, slowing down transportation networks, and also threatening health risks. The US National Weather Service said that the temperature in Manhattan would reach 91 Fahrenheit (33 Celsius) on Tuesday and will continue to rise this week. Humidity will make the heat index close to 100 Fahrenheit. The forecaster of the US Weather Forecast Center, Allison Santorelli, said on Sunday that residents will not feel too hot at night because the temperature will not drop too much. "We expect widespread record-breaking heat in the Midwest, Northeast, and Mid-Atlantic regions to occur from tomorrow," Santorelli said. "This situation will last at least until this week and may last until next weekend." As the temperature rises, electricity demand increases and the power grid and wholesale prices will come under pressure. If the rail bends due to overheating, trains may have to slow down, hindering freight and passenger transportation. Heatstroke may also increase, with the elderly, children and outdoor workers particularly vulnerable.