The important thing to remember is that we can only expect *some* relief in a best case scenario with a strong El Niño event delivering abundant precipitation across the Southwest over the winter season. Current drought conditions have accumulated over years and cannot be erased by a single wet season. We can look back at drought indices around the time of the last strong El Niño event over the winter of 1997-1998.
For a detailed look at Standardized Precipitation Index (SPI) in Arizona - Click Here
Wet conditions were observed across Arizona over several months which dramatically improved short-term drought conditions (months to seasons), but longer term drought conditions (seasons to years) were still present and quickly intensified as dry conditions returned the following year. At this point we will need several years of average to above-average precipitation over each season to alleviate long-term drought conditions. An El Niño winter with above-average precipitation would help, but is not a silver bullet at this point.
A portion of this FAQ was originally published in the CLIMAS blog on Aug 6, 2014