Temperature

Only a handful of areas in Arizona and New Mexico saw the mercury dip to below-average temperatures during the 2011 water year. The southwest deserts of Arizona were 60—75 degrees Fehrenheit, while the Colorado Plateu and the northern two-thirds of New Mexico were 40—60 degrees F (Figure 2a). In Arizona, the dividing line between the warmer temperatures to the south and the cooler temperatures to the north followed the elevation changes of the Mogollon Rim. In New Mexico the temperature gradient reflected both the paths of winter storms and the Continental Divide—temperatures are generally warmer east of the divide.

Temperatures were generally 1 degree F warmer than average across northern Arizona and between 1 and 2 degrees F warmer than average in the southern half of the state (Figure 2b). The Phoenix metropolitan area recorded temperatures between 2 to 4 degrees warmer than average. The warmer urban temperatures were largely due to the urban heat island. The area around Bagdad in west-central Arizona that appears to be 2–4 degrees colder than average is caused by a station location change rather than cold conditions. 

More dramatic warm conditions settled over the eastern third of New Mexico, including Lincoln and Otero counties, where temperatures were 4–5 degrees F warmer than average.

A major cause of the warmer conditions across both states was the La Niña event that persisted during the 2010–2011 winter. The moderate to strong La Niña caused cold winter storms to remain north of Arizona and New Mexico. The general lack of summer rain also contributed to above-average temperatures. This was particularly evident in eastern New Mexico, where a persistent ridge of high pressure inhibited monsoon storms. The high pressure created clear skies and the lack of cooling rainfall kept nighttime temperatures high, sustaining warmer daytime temperatures.
 

Click figures to enlarge.

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