[drumz0rz]

Excluding the effects of smog and pollution from cities, from a purely architectural standpoint, cities have very little impact on the weather, and mostly provide environmental changes at the ground of that city but no futher out.

For example, high rises can easily channel air and create stronger winds. You really notice this in Jersey City for example while it's less of an issue in Manhattan due to the geography of the area (winds blow across the NJ wetlands, and lose most of their strength over the hudson river).

They can also heat the ground due to the reflection of IR energy off low-E glass, and the increased thermal conductance of asphalt and concrete.

The other interesting effect is that while sky scrapers may form wind tunnels near the streets, they also act to block and track higher winds aloft. As a result, when weather such as fog rolls over a city like NY, the saturated air can cling to the buildings and trap the city in a low blanket, while the surrounding areas and rivers, the clouds pass over un-obstructed.