A History of Snowfall in Phoenix  

As metropolitan Phoenix continues to expand in size, it's becoming more common to see snowfall reports in residential areas located in the higher foothill elevations of the north valley. However in most of the city, an event that produces measurable snow is still quite rare.

The greatest amount of snow recorded at the official reporting station in Phoenix was 1.0 inch on January 20 1933, and January 21 and 22 1937.

Other times measurable snow was recorded include:

0.5 inches on February 2 1939

0.4 inches on December 21 and 22 1990

0.2 inches on March 12 1917

0.1 inches on November 28 1919

0.1 inches on December 11 1985

Trace amounts of snow have been recorded on numerous occasions.

The most recent snow of significance, in areas below 2000 feet, was on December 6 1998. Snow fell over roughly the northwest half of the valley where some  minor accumulation was reported. Sky Harbor Airport recorded 0.22 inches of precipitation that day, but only a trace of snow.

The most significant documented snowfall event in Phoenix occurred on January 21 and 22 in 1937. One inch was officially reported at the federal building at Central and Fillmore. However, up to 4 inches was reported in other parts of what is now the metro area. Snow was said to have remained in shady areas until the 24th of the month.

...and from a weather summary written by an unknown author in 1898...

In the vicinity of Phoenix while snow melted almost as fast as it fell, it is estimated the measurement would have exceeded 6 inches had the snow lain on the ground. As the meteorological records of this station extend over 3 years and during that time there is no record of snow, we depend upon tradition when saying it was the heaviest snowfall within the recollection of the oldest inhabitant.