Yeah its way more. In a field the grass is reflecting alot of the heat, or using the energy for photosynthesis. In a city the asphalt literally works like a pizza oven. All the cement and asphalt absorb all that heat and get heated to insane temperatures, and then radiate that heat outwards all evening/night.

It can be more. It can really be like hitting a wall in some cities, suddenly you're on the shitside, the change is very sudden and very dramatic, lot more than from a field to a forest.