The city can have running water while some people living there don't. Slums or homeless encampments are common the world over in large cities.

It means some people simply have no means to escape such heat and will likely die.

In the US, they sometimes open cooling centers during heat waves so homeless people and poor people have a place to go. I never went to such but they did that in Fresno and bus rides were free if you said you were going to a cooling center.

Many cities I would think. My spanish teacher lives in a big city in Venezuela and they use water tanks and electricity is rationed.

Lots. Many cities have running water for only a few hours a day.

And there may often be only one tap per 100 people in densely populated slums.