There is a nice NWS recap online of the cold temperatures at the airport, and other southeast Arizona locations, during the six day run of freezing temperatures at TUS.

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January 2013 cold wave temperature recap 

  

A cold wave, with record setting cold temperatures, enveloped southeast Arizona from January 11th through the 16th. Below is a listing of the daily highs and lows that were recorded by select locations across southeast Arizona. Many locations either tied or broke daily records with a few sites tieing or setting all-time record January low.

 http://www.wrh.noaa.gov/twc/climate/Jan2013coldwaveRECAP.php

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Since the airport is one of the warmest locations in the Tucson area, the length of the period of cold morning lows is considerably longer at other spots. Back on October 25th some farms in the lower San Pedro Valley reported their first killing frost. Here at the house, within the City of Tucson, our current spell of freezing and below morning lows began on December 27th, and there have only been three days since then with lows above freezing. This morning the low here was 31F - making the current run of below freezing mornings eight days. Imagine that the January gas bill will be quite high.