A stretch of hot weather can feel a lot hotter in the city than in the countryside. Liz, cities do tend to be warmer than the surrounding countryside.
Cities hold heat partly because concrete and pavement absorb sunlight.
But the major reason cities are warmer is that they can't easily cool down. Consider that when a dog gets hot, it pants. When you get hot, you sweat to help cool your body. Forests also sweat. But a city can't do that.