Life in the desert is tenuous, and where large cities have sprung up, supported by imported water and electricity brought in from afar, residents in cities in the middle of deserts are lulled into thinking that life there is possible even without such support. Being on stable ground, Phoenix will in the main be standing after the shift, outside of the damage done by hurricane force winds and the possibility of volcanic dust dumping or firestorms dropping from the skies. Those who plan on surviving must think about what they will do after they survive, else they will not long survive. A check into the past, at what did live there and the lifestyle required, can be an eye-opener. Where Arizona is old rock and has withstood many pole shifts without buckling, such cities as Phoenix will find the hard baked soil reluctant to garden even with torrential and continuous rains. Ground that has been baked for millennia under the hot sun is like brick, as what would not blow away in the wind as dust or wash away in flash floods has hardened.
Phoenix is circled by agriculture in places supported by water piped in from nearby rivers, and with this culture established may react to the increased rains that follow every pole shift with an attempt to produce food for the survivors. The dazed populace will lean heavily on any farms nearby, which will find themselves stripped of any edibles so that sustained agriculture is not possible. Phoenix, like most cities with high numbers of survivors, will find the human survivors like a plague of locusts, consuming everything in sight. With deserts on all sides, and travel inhibited by broken roads and bridges, travelers trying to escape this plight will likely find themselves dying of starvation before getting to lands that can support them.
See also ZetaTalk: Phoenix Lights