It's pretty amazing what has happened in Tucson over the past 20 years. What started as a small effort has grown to include policy in Tucson and is now slowly infiltrating in Phoenix (the 6th largest
city in the US and largest hot arid city in N. America). Lately I've been sitting in on meetings with the Phoenix City Council on "Complete Streets" as a representative for the stormwater harvesting aspect of the streets (green infrastructure). The Council's recommendations are nearing completion and will be sent to various departments as soon as this summer.
This type of work, while it may not look like much to those in more humid climates, is critical for those of us in urban deserts. The added load of vehicle emissions and industrial contaminants paired with lack of vegetation, can make urban deserts particularly prone to health hazards. Plus the paving over of soils with asphalt and cement means that we have vastly increased our urban heat island effect (UHI). These hard surfaces, if they are not shaded, absorb heat all day long and release it in the cooler temperatures at night - creating "higher lows". What does higher lows look like? Well, so far Phoenix holds the record for the highest low for an August day in 2013 where the LOW temperature was 96F/36C. They say we will break that record this year and have a night where it does not fall below 100F/38C. Remember, that is our "cool nighttime temperature" not the high for the day...