[Dilbert San Diego]

yes, the urban heat island phenomenon is a factor in these high temperatures.

But just because there are more man made structures absorbing heat, does not mean that the overall weather patterns have changed.

[Theoria]

Localized weather phenomena is a norm. Frost line moved down in the late 1890’s in Florida, there was once citrus further north. The additional infrastructure and peoples throughout the south west and west in general is a factor in weather conditions. That is life, and expect it to continue. Man made conditions often expand phenomena, like the dust bowls of the 30's. We've yet to see what putting millions of people and their demands in desert conditions have in such areas.